Biomedical subjects
Publications and source records attributed to A Schadel.
We present a case of a 3 8/12 years old boy with histologically proved medulloblastoma. Preoperatively a tumor of the parotid gland was diagnosed, exstirpated and interpreted as a metastasis of medulloblastoma. Therefore the opinion seems to be questionable, that extracranial metastases of medulloblastomas only occur after injury of the dura mater (operation, shunt).
A combination of cisplatin (DDP) and tumor promoter phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) or nonphorboid tumor promoter mezerein (MEZ) were tested by 5-bromo-deoxyuridine (BrdU) and 3,4,5-dimethylthiazol-2,5-disphenyl-tetrazolium bromide (MTT) assays for their antiproliferative actions. DDP and TPA showed a synergistic effect at concentrations where the single drug did not show any significant action. The BrdU assay seemed to be more sensitive than the MTT assay in measuring these drug effects. Epidermal growth factor (EGF)-receptor number and affinity on treated cells were not altered as showed by 125I-EGF-receptor assay. EGF stimulation experiments suggested an inhibition of receptor-mediated signal transduction by TPA.
Oxide ceramic materials (partial and total ossicular replacement prostheses) have been implants of preference for the reconstruction of the ossicular chain because of their excellent biocompatibility. The reaction on the surface of the implants takes place at three biodynamic levels according to the model of Stern's bilayer. We investigated the adsorption of proteins, which is determined by the cellular reaction and degradation to the surface using radial immunodiffusion and immunohistochemical methods. First, ceramic implants of aluminum oxide, hydroxyapatite, glass ceramic and zirconium oxide have individual actual (i.e. biological) surfaces. With a perthometer and the contact-free laser Focodyn method we determined each actual (i.e. biological) surface of the various ceramic implants mentioned above. Using radial immunodiffusion, the adsorption of albumin, glycoprotein, plasminogen, fibronectin, IgA, IgG and IgM shows characteristic rates of adsorption to the respective ceramic surfaces in correlating to the actual surface. A cross-check with fluorescent antibodies confirmed the protein adsorption. The individual surface adsorption of the proteins remains characteristic and is the basis for the recording of cellular reactions after implantation.
After the failure of interferon monotherapies for head and neck cancer, an increasing number of combination experiments with chemotherapy and interferons have been carried out to improve the antiproliferative effect. In vitro drug testing requires sensitive assay to detect synergistic effects of tested combinations in order not to get false-negative results. The widely used MTT assay (3,4,5-dimethylthiazol-2,5-diphenyltetrazolium bromide) and the BrdU assay 5-bromo-2-deoxyuridine were compared. It could be shown that the BrdU assay is over 10 times more sensitive and that it reflects the cell proliferation status as shown by flow-cytometric analysis using double staining with BrdU. Labeling with BrdU also allows the estimation of the S phase time. Because of the direct effect of interferons on the cell cycle, the BrdU assay could be appropriate for proliferation studies using interferons.
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