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Biomedical subjects

W Hoppe

Publications and source records attributed to W Hoppe.

At least 19 recordsLinked to original sources
PubMed1991

[Solubility of enamel and synthetic hydroxylapatite on irradiation].

The effect of Co 60-irradiation (70 Gy) on pulverized human enamel and synthetic hydroxyapatite was studied in vitro. Irradiated and non-irradiated samples were experimentally demineralized (pH 5.1) during a period of 28 days. In terms of solubility, defined as the equilibrium of saturation, there was no statistically significant difference between irradiated and non-irradiated enamel. However, in terms of solubility rates, defined as the amount of dissolved substance during the demineralization period, irradiated enamel showed a statistically significantly higher solubility rate than non-irradiated enamel. There was no effect of Co 60-irradiation on synthetic hydroxyapatite.

Dental Enamel Solubility↗
PubMed1991

[Study of properties of electrical root canal length measuring instruments].

Six electrical instruments for locating the apex during endodontic treatment were tested in a laboratory investigation about currency, frequency and scale. Further we looked, whether all instruments show coincidence in the apex point. There are great differences in currency, frequency and scale (apex point). The reproducibility and the precision of an apex locator--at the time--depends an many factors and thus indication seems to be very limited.

Dental Pulp Cavity↗
PubMed1989

Endocytosis of a small dermatan sulphate proteoglycan. Identification of binding proteins.

Endosomal preparations from human osteosarcoma cells and from fibroblasts contain 51,000- and 26,000-Mr proteins which bind a small dermatan sulphate proteoglycan after SDS/polyacrylamide-gel electrophoresis and Western blotting. Binding can be inhibited by unlabelled proteoglycan core protein. The proteins co-precipitate with a proteoglycan core protein-antibody complex. Scatchard analysis of immobilized endosomal proteins yielded a KD of about 37 nM for the proteoglycan. In intact cells proteins of the same size can be found. They are sensitive to trypsinization. A 51,000-Mr protein is the predominant membrane protein with strong binding to immobilized dermatan sulphate proteoglycan. There are additional proteoglycan-binding proteins with Mr values of around 30,000 and 14,000 which are insensitive to trypsin treatment. In contrast with the 51,000- and 26,000-Mr proteins, they resist deoxycholate/Triton X-100 extraction several days after subcultivation.

Aggrecans↗
PubMed1989

The alkalizing properties of calcium hydroxide compounds.

Calcium hydroxide compounds are available in various forms, such as in aqueous suspensions or as cements, liners, pastes or filled resins. When such compounds are exposed to water, the calcium hydroxide dissociates and the pH value shifts to the basic. In this study the compounds Pulpdent, Dycal, Hydroxyline, Gangraena Merz and Prisma VLC-Dycal were subjected to analysis, including quantitative measurement of the amount and the chronological course of ion release following exposure to water, qualitative analysis of the alkalizing effects at the dentin surface and examination of antimicrobial properties. The results showed that calcium hydroxide compounds differed greatly. The strongest degree of ion release, combined with definite antimicrobial properties, was found for the aqueous calcium hydroxide suspension (Pulpdent). The cement (Dycal) demonstrated significantly weaker activity. The liner and the paste (Hydroxyline and Gangraena Merz), as well as the calcium hydroxide filled resin (Prisma VLC-Dycal), were largely lacking in both ion release and antimicrobial properties under the experimental conditions.

Calcium Hydroxide↗
PubMed1988

Degradation of endocytosed dermatan sulfate proteoglycan in human fibroblasts.

Endocytosis and subsequent degradation of iduronic acid-rich small dermatan sulfate proteoglycan from fibroblast secretions were studied in human fibroblasts. Upon endocytosis of [3H]leucine- and [35S]sulfate-labeled proteoglycan release of free leucine was 10 to 15 times more rapid than that of inorganic sulfate. Within approximately 3 h a steady state was approached between transport of proteoglycan to the compartment of core protein degradation and release of free leucine. No such steady state could be found with respect to the dermatan sulfate chains. In the presence of benzyloxycarbonyl-Phe-Ala-diazomethylketone or of other SH-protease inhibitors the degradation of the protein moiety of endocytosed proteoglycan was much less inhibited than the degradation of the polysaccharide chain. Benzyloxycarbonyl-Phe-Ala-diazomethylketone did not affect the degradation of dermatan sulfate chains taken up by fluid phase endocytosis and the activities of all known dermatan sulfate-degrading enzymes. Percoll gradient centrifugation indicated that also in the presence of the protease inhibitor the partially degraded proteoglycan accumulated in dense lysosomes. The isolation of intracellular dermatan sulfate peptides and molecular size determinations of endocytosed dermatan sulfate proteoglycan supported the conclusion that a critical proteolytic step is required before the dermatan sulfate chain becomes accessible to hydrolytic enzymes.

Ammonium Chloride↗
PubMed1986

Negatively stained 50 S ribosomal subunits of Escherichia coli.

Ribosomes are large nucleoproteins of approximately 3 X 10(6) Mr. In contrast to helical or spherical nucleoproteins (viruses) of similar size (which consist of several hundred small asymmetric units reproduced by symmetry), ribosomes are completely asymmetric; therefore, the amount of structural information (defined by the number of independent image elements) necessarily increases from about 10 to 20 to about 1000 to 2000 (at resolutions of the order of 2 nm). With present techniques, only stained single particles can be studied in the electron microscope. Our published work on the 30 S subunit and on the 50 S subunit has demonstrated that three-dimensional reconstructions of stained single particles show a great number of structural details that are reproducible if the particles have the same orientation. One of the main results of this paper is the final proof of this reproducibility from detailed comparisons of individual 50 S subunits and of independent averages over a few (3 to 5) particles in the kidney or crown orientation; in the latter case, even after a chemical modification. The 50 S subunit is non-uniformly stained along the optical axis. It displays a complicated, stain-filled channel-like structure, within which is approximately the partial volume expected for the RNA. The particle shows an irregular but reproducible boundary surface against the stain. At several sites, the channel structure protrudes to the surface. Since the secondary structure of the RNA is well known, one might try to locate it in the subunit after chemical identification of its surface contacts (the 3' end of 23 S RNA and the 3' end of the 5 S RNA have been localized). Most interesting is a groove on the surface, which might accommodate the mRNA.

Computer Simulation↗
PubMed1986

Post-translational phosphorylation of proteodermatan sulfate.

In cultured human skin fibroblasts, the core protein of the small proteodermatan sulfate becomes phosphorylated post-translationally but before the glycosaminoglycan chains are synthesized. This phosphorylation can occur when the intracellular transport is inhibited by carbonyl cyanide m-chlorophenylhydrazone or when the attachment of asparagine-linked oligosaccharides is prevented by tunicamycin. Serine and glycosaminoglycan chains were identified as phosphorylation sites of secreted proteodermatan sulfate. Upon alkaline borohydride treatment and degradation by chondroitin ABC lyase, the main phosphorylated product co-chromatographed with an unsulfated 3H-labeled hexasaccharide prepared analogously from [3H]galactose/[35S]sulfate-labeled proteodermatan sulfate.

Cells, Cultured↗