Über künstlich erzeugte Janusbildungen von Triton taeniatus

Ohne Zusammenfassung     

Modelluntersuchungen zur fermentativen Löslichkeit von Fibrin im histologischen Schnitt

Zusammenfassung Es wird ein Verfahren beschrieben, das es gestattet, die fermentative Einwirkung verschiedener Proteasen auf histologische Schnitte von Fibrinpräparaten unter konstanten Bedingungen kontinuierlich zu beobachten und zu photographieren. Histologische Schnitte von Rinderfibrin sind mit den Proteasen Pepsin, Papain, Trypsin, Chymotrypsin und Plasmin, jedoch nicht mit Kollagenase aufzulösen. Lichtmikroskopisch zerfällt das Fibrinnetz nach Einwirkung von Trypsin, Chymotrypsin und Plasmin in kleine Granula, während es nach Einwirkung von Pepsin langsam unter Erhaltung der Netzstruktur verdämmert. Für dieses verschiedene Verhalten werden Beziehungen zwischen Fibrinstruktur und Spezifität der einzelnen Proteasen diskutiert. Eine vorherige Formalinfixierung des Fibrins macht jede fermentative Proteolyse durch chemische Veränderungen am Substrat unmöglich, während alkoholisch fixierte Fibrinschnitte durch Chymotrypsin, Trypsin und Plasmin und weniger gut durch Pepsin und Papain zur Auflösung gebracht werden können. Die Alkoholfixierung blockiert jedoch das am Fibrin adsorbierte Plasminogen weitgehend, so daß eine fermentative Löslichkeit durch Streptokinase und Proaktivatorzusatz allein nicht gelingt.

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Summary A method is described which allows to observe and photograph continously the enzymatic action of various proteases on histologic sections of fibrin under constant conditions. Histologic sections of fibrin (cattle) are dissolved by pepsin, papain, trypsin, chymotrypsin, and plasmin, whereas collagenase has no effect whatsoerver. After treatment with trypsin, chymotrypsin, and plasmin the fibrin-net disintigrates and light-microscopally appears as small granules. After treatment with pepsin the net-like structure is maintained, but fades slowly away. Because of this observation the relation between the structure of the fibrin and the specificity of the various proteases is discussed. Fixation of the fibrin with formalin inhibits any enzymatic proteolysis through a chemical change of the substrate, whereas alcohol fixed fibrin sections are dissolved by chymotrypsin, trypsin, and plasmin. The effect of pepsin and papain on the fibrin is slightly reduced. Plasminogen, which is absorbed to the fibrin, is blocked to a large extent by alcohol fixation. An enzymatic dissolution by streptokinase and pro-activator is therefore impossible.

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Mit Unterstützung der Deutschen Forschungsgemeinschaft.     

A431 cell variants lacking the blood group A antigen display increased high affinity epidermal growth factor-receptor number, protein-tyrosine kinase activity, and receptor turnover

The epidermal growth factor receptor (EGF-R) of human A431 cells bears an antigenic determinant that is closely related to the human blood group A carbohydrate structure. Labeling studies with blood group A reactive anti-EGF-R monoclonal antibodies and various lectins revealed that A431 cultures are heterogeneous with respect to blood group A expression. We have isolated clonal variants of these cells that either express (A431A+ cells) or completely lack (A431A- cells) the blood group A specific N-acetyl-D-galactosamine (GalNAc) residue. We show that this difference is due to the absence of a UDP-GalNAc:Gal transferase activity in A431A- cells. Subsequently, we have compared EGF-R functioning in these cell lines. Scatchard analysis of EGF-binding shows that in A431A- cells 6.3% of the EGF-R belongs to a high affinity subclass (Kd = 0.4 nM) while in A431A+ this subclass represents only 3.2% of the total receptor pool. The elevated level of high affinity receptors in A431A- cells is accompanied by a parallel increase in receptor protein- tyrosine kinase activity. In membrane preparations of A431A- cells, receptor autophosphorylation as well as phosphorylation of a tyrosine-containing peptide substrate is 2-3-fold higher as compared with A431A+ cells. In intact A431A-cells, the difference in receptor activity is measured as a 2-3-fold elevated level of receptor phosphorylation and a 2-3-fold higher abundance of phosphotyrosine in total cellular protein in A431A- cells. In addition, [35S]methionine pulse-chase experiments showed a ligand-independent increase in turnover of EGF-R in A431A- cells: the receptor's half life in these cells is 10 h as compared with 17 h in A431A+ cells. Our results suggest a possible involvement of GalNAc residue(s) in determining EGF-R affinity, protein-tyrosine kinase activity and turnover in A431 cells. Furthermore, our results indicate that high affinity EGF-R are the biologically active species with respect to protein-tyrosine kinase activity.     

Identification of EBV-DNA in lymph nodes from patients with lymphadenopathy and lymphomas associated with AIDS

Fourteen examples of non-Hodgkin’s lymphoma (NHL) and four of Hodgkin’s disease in patients with AIDS as well as lymph nodes exhibiting changes related to the lymphadenopathy syndrome (LAS) from 11 HIV-positive individuals were studied for the presence of Epstein-Barr virus (EBV) genome both by in situ DNA hybridization and blotting techniques. Both methods were performed using formalin-fixed paraffin-embedded material. All the NHLs were of high malignancy and all but one were of the B-cell type. Of the four examples of Hodgkin’s disease, two were lymphocytic predominant, one of mixed cellularity and one of the nodular sclerosing variety. The lymph nodes of patients with LAS were mostly stage I with marked follicular hyperplasia. In 7 of the 14 NHLs the presence of EBV-DNA was clearly demonstrated by dot-blotting and by in situ hybridization. All lymph nodes from the patients with LAS and AIDS-related Hodgkin’s disease were negative for EBV by dot-blot and in situ hybridization assays. We conclude that EBV plays a role in the development of AIDS-related lymphomas, but the fact that half these lymphomas are EBV-negative suggests that other mechanisms such as polyclonal stimulation of B-cells by HIV products may also be important. This study was supported by the DFG, SFB 172 to BBC and HKMH and by the BMFT grant 01KI 88061 to BBC     

Novel histamine H3 receptor antagonists based on the 4-[(1H-imidazol-4-yl)methyl]piperidine scaffold

We report the discovery of novel histamine H(3) receptor antagonists based on 4-[(1H-imidazol-4-yl)methyl]piperidine. The most potent compounds in the series (e.g., 7) result from the attachment of a substituted aniline amide to the main pharmacophore piperidine via a two-methylene linker.