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Biomedical subjects

A Wohlwend

Publications and source records attributed to A Wohlwend.

53 records · Page 3Linked to original sources
PubMed1985

Calcitonin and calcitonin gene-related peptide interact with the same receptor in cultured LLC-PK1 kidney cells.

Calcitonin and calcitonin gene-related peptide stimulate adenylate cyclase activity and plasminogen activator production in cultured renal tubular LLC-PK1 cells. Salmon [125I]calcitonin and human [125I]calcitonin gene-related peptide bound specifically to the cells. Salmon [125I]calcitonin binding was reduced at lower concentrations of non-radioactive salmon calcitonin than of human calcitonin gene-related peptide. For the stimulation of adenylate cyclase activity and plasminogen activator production, the potency of salmon calcitonin was higher than that of human calcitonin and calcitonin gene-related peptide. In a subclone of LLC-PK cells lacking salmon calcitonin binding sites, no specific binding of [125I]CGRP occurred, and adenylate cyclase activity and plasminogen activator production was not increased by the peptides. Thus, in LLC-PK1 cells the stimulation of adenylate cyclase activity and plasminogen activator production by calcitonin gene-related peptide is probably mediated by the calcitonin receptor.

Adenylyl Cyclases↗
PubMed1985

LLC-PK1 cysts: a model for the study of epithelial polarity.

In the present work, we have taken advantage of the properties of two recently isolated clonal subpopulations of the pig kidney-derived LLC-PK1 cell line to study aspects of the establishment of epithelial polarity. When grown in suspension, LLC-PK1/D + Sc cells reaggregated within a few hours and, during the following days of culture, formed free-floating, hollow spheres or cysts, lined by a monolayer of polarized cells. In contrast, LLC-PK1/D- cells were unable to develop such polarized structures even upon prolonged culture in suspension. The polarity of the LLC-PK1/D + Sc cells lining the cysts was inverted compared to that in intact renal tubules, the microvilli-rich "apical" pole being oriented toward the external medium. However, upon embedding these preformed cysts in collagen gels, a reversal of polarity was observed within hours, the microvilli-rich pole now facing the cyst cavity. Thus, in the same clonally derived cell population, cell-to-cell contact and interaction with the extracellular matrix differentially affect the orientation of cellular polarity. The LLC-PK1/D + Sc cysts provide a suitable in vitro model system for further study of the sequential events by which extracellular matrix components induce an appropriately oriented polarization. In addition, the comparison between LLC-PK1/D + Sc and D- cells, which differ in their ability to polarize in response to cell-to-cell contact, should help define some of the cellular determinants involved in epithelial organization.

Animals↗
PubMed1984

Concomitant secretion of prourokinase and of a plasminogen activator-specific inhibitor by cultured human monocytes-macrophages.

The plasminogen activator (PA) produced by freshly purified human monocytes-macrophages and histiocytic, lymphoma-derived U 937 cells was analyzed by zymography after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and found to migrate with an apparent Mr of 55,000, identical to that of urokinase (Uk). By immunoprecipitation with antibodies specific for the two different types of PA, the enzyme was shown to be immunologically related to urokinase, and not to tissue PA. Urokinase was secreted in the form of the inactive Mr 55,000 zymogen prourokinase , and could be converted to the active Mr 55,000 enzyme by limited proteolysis with plasmin. Conditioned media from cultures of U 937 cells and monocytes-macrophages inhibited the fibrinolytic activity of exogenously added urokinase. Using [125I]-labeled urokinase we observed the formation of an enzyme-ligand complex, which was not dissociated by boiling in SDS and migrated with an apparent Mr 40,000 daltons higher than the free enzyme; since complexed urokinase was functionally inactivated as a PA, the ligand is an inhibitor of urokinase. This inhibitor is different from fibroblast-produced protease- nexin , in that it did not interact with thrombin. These results suggest that plasminogen activation by mononuclear phagocytes can be modulated through the secretion of both (pro)enzyme and a specific inhibitor.

Cell Line↗
PubMed1983

[Ultrastructural detection of the heterogeneity of glycocalyx in convoluted and straight proximal tubules of rat kidney by the lectin-gold complex technic].

A new histochemical technique in which lectin-gold complexes are applied directly to thin and semi-thin sections of tissue was used to determine the distribution of Helix pomatia lectin binding sites in the proximal tubule of Rat kidney. Whereas a strong labeling was seen on the brush border and baso-lateral plasma membranes of convoluted tubules, the plasma membrane of cells from the medullary straight segment was unlabeled. Some profiles at the frontier between cortex and medulla had a mosaic of positive and negative cells. These results show, therefore, considerable segmental variation in the glycocalyx composition of Rat proximal tubules.

Animals↗
PubMedDate not supplied

Evidence for polarization of plasma membrane domains in pancreatic endocrine cells.

Polarization of plasma membrane domains is an essential feature of secretory epithelial cells from exocrine glands. The surface of exocrine cells (a typical example is the acinar cell of the pancreas) is separated into an apical domain, where secretion occurs by exocytosis, and a basolateral domain, which senses variations of the internal milieu and is enriched with receptors for various hormones and secretagogues. It is unknown whether secretion is polarized in endocrine cells (except for thyroid follicular cells, which are organized into cavitary structures). To determine whether distinct plasma membrane domains exist in endocrine cells, we infected monolayer cultures of pancreatic endocrine cells with enveloped RNA viruses known to bud selectively from either the apical or basolateral domain in polarized epithelial cells. This asymmetrical budding is thought to reflect the polarized nature of the infected cells, as in non-polarized cells such as fibroblasts, the same viruses bud nonselectively from the entire cell surface. We show here that influenza virus and vesicular stomatitis virus (VSV) emerge asymmetrically from cultured pancreatic islet cells; this represents the first evidence for polarization of plasma membrane domains in pancreatic endocrine cells.

Animals↗
PubMedDate not supplied

Heat-pressed ceramics: technology and strength.

The flexural strength of a new heat-pressed ceramic material (IPS-Empress) was measured before and after pressing and/or simulated firing treatments (eg, veneering, surface coloring, glazing). Heat pressing the material significantly improved its flexure strength whereas heat treating the material alone did not. Additional firings (heat treatments) after heat pressing further increased material strength. The final strength values ranged between 160 and 180 MPa and were comparable to some other all-ceramic systems. No clinical implications were drawn from these data.

Aluminum Silicates↗
PubMedDate not supplied

Metal ceramic and all-porcelain restorations: current considerations.

A review of the state of the art of metal ceramic and all-porcelain restorations is made. Metal ceramic systems are discussed relative to current fabrication techniques, porcelain margin techniques, marginal adaptation, and esthetics. The material properties, marginal adaptation, and esthetics of all-porcelain restorations are reviewed. Additionally, observations of metal ceramic and all-porcelain restorative systems currently in development are presented.

Ceramics↗
PubMedDate not supplied

Maxillary anterior single-tooth replacement: comparison of three treatment modalities.

The correct treatment of a single missing maxillary anterior tooth in the aesthetically prominent area has become more challenging. The missing tooth can today be replaced by one of three prosthodontic treatment modalities--conventional fixed bridge, resin-bonded bridge, and single-tooth implant. The most important factors to be considered are the predictability of aesthetics, the preservation of the enamel shield and the dentinal and pulpal tissue, and the preservation of the periodontium and the alveolar bone. The learning objective of this article is a critical discussion of these three modalities as a replacement of a missing anterior single tooth to aid in selection of the most appropriate treatment in each individual clinical case.

Dental Implants↗