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W Villiger

Publications and source records attributed to W Villiger.

At least 37 records · Page 2Linked to original sources
PubMed1980

Antigen-independent binding of IgG dimers to C 1 q as studied by sedimentation equilibrium, complement fixation and electron microscopy.

Rabbit anti-SII pneumococcal polysaccharide IgG antibody was cross-linked by dithiobis (succinimidyl propionate). The IgG dimers were visualized by electronmicroscopy and resembled two Y-shaped structures connected in random orientations. The three arms of the Y's were of equal length. The six globular domains of the IgG protomers could be seen, but the Fab arms and Fc stems could not be distinguished from each other. Electron microscopy revealed that the dimers were bound to the globular heads of C 1 q. From the dependence of thee weight average molecular weight on dimer concentration, and equilibrium constant of about 10(6) M(-1) was derived for the binding of dimers to C 1 q. The number of IgG dimers which could be accommodated at a single C 1 q molecule was derived to be three. The data do not allow a clear distinction between noncooperative and cooperative binding. The binding equilibrium was independent of whether the IgG dimers were liganded with an SII nonasaccharide hapten or not. The results are at variance with an allosteric mechanism of the action of antigen in C1 activation. They lend support to the association hypothesis of complement activation. The data suggest that clusters of about six IgG molecules, connected by a multivalent antigen or arranged at the cell surface, are recognized by C 1 q with a binding constant of about 10(10) M(-1).

Animals↗
PubMed1980

Assembly of subcomponents C1r and C1s of first component of complement: electron microscopic and ultracentrifugal studies.

Monomeric C1s (Mr, 85,000; s20,w, 4.3S), a subcomponent of first component of complement (C1), the dimer (Mr, 170,000; s20,w, 6.7 S) of C1r, another subcomponent, and the tetrameric complex (C1r,C1s)2 (Mr, 340,000; s20,w, 8.7 S) are elongated molecules. Hydrodynamic equivalents of cylindrical shape have a diameter of 3.3 nm and lengths of 20 nm for C1s, 36 nm for (C1r)2, and 64 nm for (C1r,C1s)2. In electron micrographs the C1r,C1s complex appears as a chain composed of six to eight globular domains with a contour length of 51 nm. A structure is proposed in which (C1r)2 forms a core to which C1s protomers are associated at both ends. The C1 complex (s20,w, 16.3 S) reconstituted from C1q, C1r, and C1s dissociates under the conditions used for electron microscopy. Some features of the C1 complex are revealed in the dissociation products.

Centrifugation, Density Gradient↗
PubMed1979

[The ultrastructure of the endings of nerve fibers of ordinary hairs of mammals under normal conditions and during degeneration and regeneration].

At ultrastructural level, three zones are distinguished of the palisade endings of nerve fibers, most of them in contact with the basement membrane of the outer epithelial sheath of the radix pili on rat muzzle. After division of the supplying nerve (n. infraorbitalis) in test animals of the same species, its nerve fibers and palisade endings undergo degeneration, followed by regeneration within 4-5 months. Changes in the ultrastructure of the mentioned nerve elements are thoroughly studied and demonstrated in the course of the two processes. While within 6...12 days of the operation, the palisade endings degenerate, 130 days after the intervention most of them are restored and exhibit an appreciable difference relative to their typical ultrastructure in normal state. The Schwann's cells processes, enveloping degenerated and regenerated palisade endings, similarly display marked fine-structure alterations.

Animals↗
PubMed1975

Glycogen in epidermal nerve terminals of Lacerta sicula (squamata: reptilia).

Proof is given that the granula occuring in the epidermal discoid nerve terminals of Lacerta sicula consist of glycogen. Staining with PA-PbCi shows 300 A sized alpha-particles and 70 A sized beta-particles. The electron-dense boundary appearing after digestion with alpha-amylase consists of limit-dextrins.

Animals↗
PubMed1975

Chemical analysis and electron microscopy studies of human C1q prepared by different methods.

Five differently isolated and purified human C1q preparations were examined by electron microscopy and analyzed by polyacrylamide gel electrophoresis in 0.1% sodium dodecyl sulfate and 0.5 M urea. The amino acid and carbohydrate composition of C1q purified by the DNA method are reported and compared with results obtained on C1q isolated by other procedures. Electron microscopy showed that all C1q preparations had six peripheral subunits connected by fibrillar strands to a central subunit. The presence of small amounts of dimers was also observed. The physico-chemical properties of the molecule are independent of the purification method used. The five C1q preparations labeled with 125I in presence of lactoperoxidase formed two types of noncovalently linked subunits. In each case the smaller (central) subunit contained over thirty times as much radioactivity as the larger (peripheral) subunit supposed to interact with immune complexes. Reduction and alkylation confirmed for each preparation the presence of three polypeptide chains, the smaller of which contained essentially all radioactivity.

Amino Acids↗
PubMed1975

[Ultrastructural studies on an animal model of epiphyseolysis. Cells and matrix in the proximal growth plate of the rat tibia after administration of DL-serine(3,4,5-trihydroxybenzyl)-hydrazide] (author's transl)

After administration of DL-serine-(2,3,4-trihydroxybenzyl-)hydrazide, the growth plate of rat tibia, and most of all the zone of hypertrophic cartilage, is much widened. Numerous chondrocytes become necrotic, and their columnar arrangement disappears. There is no zone vascular invasion. Spontaneous epiphyseolyses occur frequently, The ergastoplasm is damaged most; it is dilated and forms giant and/or collapsed cisternae. At a later stage it is reduced to a few vesicles. It is assumed that the chondrocytic synthesis and secretion are disturbed. The loss of cytoplasmic processes also confirms this. In the cartilage matrix there are broad collagen fibres of an axial periodicity of 650 A, which are atypical of hyaline cartilage. Possible pathogenetic mechanisms of the distrubed fibrillogenesis are discussed in conncetion with the epiphyseolysis.

Animals↗
PubMed1973

A scanning and transmission electron microscope study of antigen-binding sites on rosette-forming cells.

The ultrastructure of binding sites in rosette-forming cells of mice after immunization with sheep red cells was studied by means of scanning and transmission electron microscopy. It was found that the red cells were bound to the lymphocyte surface in circumscribed, immunoglobulin-containing areas, consistent with a spotlike or patchy distribution of antigen-binding immunoglobulin receptors. In these contact areas the cell membranes formed a gap of 80 A (range 75-90 A) which exhibited electron-opaque bridges at high magnification. These results are discussed in the light of the recent recognition of the formation of immunoglobulin spots on the lymphocyte surface after antigen contact. Morphological details suggest that the same mechanism is operating in rosette formation, possibly including the movement of the contact areas on the lymphocyte membrane.

Animals↗