Das Zerfallsstadium und die Folgen der Mastzelldegranulierung mit besonderer Berücksichtigung der mesenchymalen Reaktion

Zusammenfassung Die Injektion des MZ-Degranulators (Histaminliberator) 48/80 in einem MZ-reichen Gewebe führt über die Aktivierung der Granulabildung in den MZ zur Entleerung der neugebildeten Granula (Orfanos und Stüttgen 1962). Die bei niedriger 48/80-Dosis beobachtete lokale Entleerung ohne Zelldestruktion wird bei Erhöhung der verabreichten 48/80-Dosis zu einem abrupt eintretenden Zellzerfall. Dabei werden die vorausgehenden proliferativen Prozesse unterbrochen und unreife Granula ins Interstitium entleert.Das Zerfallsstadium der MZ-Granulation zeigt charakteristische Gewebeveränderungen, die näher beschrieben und erläutert werden (Leukozyteneinwanderung, Eosinophilie, Granulocyten-essaimage, Aktivierung der Fibrillogenese, Bindegewebe- und Gefäßreaktionen). Besonders beachtenswert erscheinen die Struktur und der unterschiedliche Entleerungsmodus der MZz (sekretorische Degranulierung) im Gegensatz zur eosinophilen und neutrophilen essaimage, ferner Bauweise und Schicksal der ausgeschütteten Granula sowie ihr Eingreifen in humorale und mesenchymale Reaktionen (cytotaktische Reaktion, lokale Mesenchym-Reaktion).Die Kollagenneubildung (Fibrillogenese) ist im Zusammenhang mit der MZ-Degranulierung deutlich erfaßbar und wird besonders abgehandelt. Morphologische Studien lassen als sicher erscheinen, daß die TC-Molekülbildung und zumindest die ersten Stufen ihrer linearen Polymerisierung zu den feinen Protofibrillenfäden intrazellulär erfolgen. Die laterale Aggregation zu den quergestreiften reifen Kollagenfibrillen und ihre Bündelung finden nur extrazellulär statt. Die extrazellulären Prozesse werden durch die interstitiellenph- und Ionenstärkeverhältnisse beeinflußt. Dabei spielen die sauren Sulfatgruppen der SMPS eine maßgebende Rolle.Die beschriebenen Folgen einer massiven MZ-Degranulierung können zum großen Teil als histaminbzw. heparinbedingte Prozesse interpretiert werden.     

Structural and functional stability of the mature transferrin receptor from human placenta

The transferrin receptor (TfR) is a N- and O-glycosylated transmembrane protein mediating the cellular iron uptake by binding and internalization of diferric transferrin. In this study, rate constants and dissociation constants of 125I-ferri-transferrin binding to the human TfR were examined dependent on receptor glycan composition, pH, bivalent cations, and temperature. To do so, purified human placental TfR was noncovalently immobilized to polystyrene surfaces and subjected to alterations in various parameters. We found that transferrin binding was clearly dependent on a receptor pretreatment with buffers of various pH in that most of the TfR molecules irreversibly lost transferrin binding activity below pH 6.5. However, the dissociation constant of the remaining active binding sites was not affected. Similarly, we were able to define the thermal stability of the receptor as a function of transferrin binding ability. Binding of transferrin was completely lost provided that the receptor was pretreated at temperatures of at least 65 degrees C. Treatment with EDTA also caused an irreversible loss of transferrin binding activity, indicating that the functionally active conformation of the mature TfR depends on bivalent cations. In order to examine the role of the receptor glycans, we enzymatically removed the sialic acid residues, the hybrid and oligomannosidic N-glycans, or all types of N-glycans. In contrast to the parameters described above, all desialylated and N-deglycosylated TfR variants had exactly the same transferrin binding properties as the native TfR. To assess changes in the secondary structure of the receptor, circular dichroic spectra were recorded from TfR at pH 5.0, from heat pretreated receptor and from deglycosylated TfR. Since the receptor did not exhibit detectable changes in the CD spectrum of the deglycosylated receptor, it can be concluded that the N-linked carbohydrates of the mature, fully processed TfR are not essential for transferrin binding and conformational stability.     

Morphological and functional evaluation of angiogenesis of a xenografted human sarcoma in nude mice

The implantation of tumour cells in normal tissues and the subsequent induction of angiogenesis by the growing xenograft were studied by means of immunohistochemistry and digital image analysis. Tumour growth was induced by injection of a human spindle cell sarcoma (ES3) into the subcutis of HsdCpb:NMRI-nu/nu mice. In vivo injection of Hoechst 33342 was used as a marker of perfusion. The vasculature was stained with specific antibodies and subsequently analysed by digital image analysis. Starting at day 3 up to day 6, angiogenesis could be detected and the relative amount of perfusion within the investigated area reached a peak at day 6. This method, which allows investigation of both functional and morphometric characteristics of human xenograft vasculature, serves as an excellent assay for evaluation of antiangiogenic therapies in translational research of experimental tumours.     

Gluten,a lectin with oligomannosyl specificity and the causative agent of gluten-sensitive enteropathy

The pathogenesis of gluten-sensitive enteropathy or coeliac disease is as yet unknown. We can demonstrate by laser nephelometric measurements that gluten has lectin-like properties. Gluten binds ‘high-mannose type’ glycoproteins and the complex formation is inhibitable by mannan. As known for other lectins the reaction is absolutely Ca-dependent. Glycoproteins from the immature crypt cells from the small intestine are highly more reactive than glycoproteins from the mature villous zone. The possibility of a genetically determined deficiency of the growth-dependent N-acetyl-glucosaminyltransferase-1 as the pathogenic factor of the gluten-sensitive enteropathy is discussed.     

Lectin specificity and binding characteristics of human C-reactive protein.

C-reactive protein (CRP) is thought to play an important role in immunomodulation. The exact biologic function of this pentraxin protein is, however, still unclear. Here we report experiments designed to further characterize the binding properties of CRP. Using purified human CRP it could be shown that CRP immobilized onto polystyrene surfaces or onto latex beads binds distinct plasma glycoproteins including IgG, asialofetuin, asialo-beta 2-glycoprotein I and, likewise, synthetic glycoproteins as a lectin, exhibiting binding specificity for terminal galactosyl residues of the glycoprotein glycans. Binding of CRP to IgA, IgM, IgG, asialofetuin, asialo-beta 2-glycoprotein I and to synthetic glycoproteins requires immobilization onto surfaces of both CRP and the ligand. Fibronectin and fibrinogen are bound by surface-immobilized CRP also in soluble phase. Comparing various mono-, di-, and trisaccharides as competitive inhibitors of the lectin binding activity of CRP, only beta-D-Gal-(1-3)-D-GalNAc, beta-D-Gal-(1-4)-D-GalNAc, and beta-D-Gal-(1-4)-beta-D-Gal-(1-4)-D-GlcNAc had significant inhibitory power at a concentration of 8 mmol/liter. Binding activity of CRP was pH-dependent with an optimum at pH 5 to 6 and was reduced by 90% when pH was shifted from 6 to the physiologic pH value of 7.4. CRP exhibited lectin-like properties with binding specificity for galactosyl residues also when bound to K-562 erythroleukemia cells. It is therefore suggested that CRP immobilized onto surfaces exhibits lectin activity toward galactosyl groups preferentially in a mildly acidic environment as present at sites of inflammation.