Biomedical subjects

B Scheer

Publications and source records attributed to B Scheer.

18 recordsLinked to original sources

PubMed1996

Half a century of fluoridation.

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Fluoridation↗

PubMed1995

Unpredictable teeth.

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Dental Pulp Necrosis↗

PubMed1995

An in vitro investigation into the shear bond strengths of two dentine-bonding agents used in the reattachment of incisal edge fragments.

This in vitro study investigated the shear bond strengths of sectioned bovine incisal edge fragments reattached using Gluma 2000 and Scotchbond 2. Teeth were sectioned 3 mm from the incisal edge using an Acutome with a 0.5 mm diamond wheel running at 90 degrees to the mesial or distal surface of the tooth. Twenty four incisal fragments were rebonded with each of the dentine bonding agents; a further 24 intact incisors were used as a control group. The control group required a mean fracture force of 940(+/- 144) N which was significantly greater (p < 0.01) than that required to fracture fragments rebonded using GLUMA 2000 (609 +/- 116) N and Scotchbond 2 (393 +/- 97) N. The mean force required to fracture incisal fragments rebonded with GLUMA 2000 was significantly greater (p < 0.01) than that required to fracture incisal fragments rebonded with Scotchbond 2.

Animals↗

PubMed1993

Dihydrolipoic acid prevents hypoxic/reoxygenation and peroxidative damage in rat heart mitochondria.

Fluorescence anisotropy (r) was determined in hypoxic/reoxygenating rat heart mitochondria by means of 1,6-diphenyl-1,3,5-hexatriene. During hypoxia, values for r increased, indicating a rigidified membrane. Membrane fluidity was increased when 20 pmol to 2 nmol/mg protein of dihydrolipoic acid (DHL) was present during hypoxia. Dithiothreitol (DTT) or 2-mercaptopropionylglycin (MPG) at similar concentration did not result in membrane fluidization under these conditions. Peroxidative damage was induced in mitochondria by H2O2. In the presence of 2 nmol/mg protein of DHL, malondialdehyde production was decreased by 50%. DTT or MPG brought about only a 25% decrease. These results were corroborated by spin label studies with 4-maleimido-TEMPO and 5-proxylnonane (5-P-9); H2O2 induced a decrease in fluidity in the region of labeled thiol groups and an increase in polarity sensed by 5-P-9. DHL proved efficient in reducing such fluidity and polarity changes.

Animals↗

PubMed1993

Repetitive sequences in the genome of Anemone blanda: identification of tandem arrays and of dispersed repeats.

A tandemly repetitive sequence family (AbS1) and a repetitive sequence (Hd) forming part of a larger dispersed element (dorf-1) of Anemone blanda were characterised. The AbS1 satellite sequence family is located in all 4',6-diamidino-2-phenylindole (DAPI) positive intercalary heterochromatic bands and in the DAPI positive heterochromatic terminal region of chromosome 3, while the dispersed Hd homologous sequences are preferentially associated with euchromatic chromosome regions. The major component of the AbS1 satellite is AbS1-H1 with a basic repeat unit of 1640 bp; a minor fraction (AbS1-H5) consists of 320 bp units. A subsection of the AbS1-H1 repeat unit exhibits homologies to the 25S rRNA gene of flowering plants suggesting that the 1.64 kb satellite was generated by amplification of a precursor satellite and/or single copy sequence together with an rDNA fragment. The rDNA homologous region is considered to evolve at a rate similar to pseudogenes and thus the age of this satellite DNA fraction can be roughly estimated as about 27 million years. The dispersed repeated sequence Hd (about 1300 bp) is associated with the 8 kb element dorf-1. A. blanda dorf-1 constitutes about 0.2% of the genome (3 x 10(4) copies), is bounded by identical long terminal repeats, and exhibits partial homology to the Lilium gypsy-type element del1, but has yet to be confirmed as a retrotransposon. In contrast to the AbS1 satellite sequence family, Hd homologous sequences were found not only in A. apennina, the closest relative of A. blanda, but also in A. nemorosa and A. ranunculoides indicating that a progenitor sequence of dorf-1 was present in a common ancestor before speciation occurred.

Base Sequence↗

PubMed1990

Binding of IL-1 beta to alpha-macroglobulins and release by thioredoxin.

Human alpha 2-macroglobulin (H alpha 2M) is a major IL-1 beta binding plasma protein. The characteristics of the H alpha 2M IL-1 beta complex formation suggested, that cleavage of the internal thiol ester in other members of the alpha-macroglobulin family (alpha M) could enable these proteins to bind IL-1 beta. Characterization of optimal conditions for binding 125I IL-1 beta to H alpha 2M showed that H alpha 2M-IL-1 beta complex formation could be obtained over a pH range of 6.3 to 9 in the presence of some metal cations (i.e., Zn2+, Cd2+, Cu2+, Ni2+). Other divalent metal cations (i.e., Mn2+, Mg2+, Ca2+) were without effect. Time kinetic studies showed that binding of IL-1 beta to H alpha 2M was complete within 200 min and that H alpha 2M-IL-1 beta complexes became increasingly resistant to dissociation by boiling in SDS as a function of incubation time. Human pregnancy zone protein, rat alpha 1-, alpha 2-macroglobulin (R alpha 1M, R alpha 2M), all homologous with H alpha 2M, were tested for their ability to bind IL-1 beta. In each instance, alpha M-IL-1 beta complex formation was observed only after treatment of alpha M with methylamine, a primary amine that causes cleavage of the internal thiol ester in alpha M and the appearance of free thiol groups. Similarly, for each of these proteins, complex formation was increased several fold in the presence of Zn2+. Competition experiments using cytokines or proteins of similar molecular mass as IL-1 beta established that only unlabeled IL-1 beta was effective in inhibiting binding of 125I IL-1 beta to H"F" alpha 2M. Acylation of H"F" alpha 2M by diethylpyrocarbonate blocked the binding of IL-1 beta when analyzed by native PAGE. Deacylation of H"F" alpha 2M with hydroxylamine partially restored the binding capacity of H"F" alpha 2M further supporting the involvement of histidyl residues in the Zn2(+)-dependent binding of IL-1 beta. Reduced thioredoxin, but not its alkylated form, from Escherichia coli readily releases H"F" alpha 2M bound IL-1 beta under conditions that did not lead to reduction of disulfide bonds in H"F" alpha 2M. The action of thioredoxin also augmented IL-1-like activity in two independent bioassays suggesting that H"F" alpha 2M bound IL-1 beta is partially biologically inactive or latent. These results suggest that "activated" alpha M exert a modulating role for IL-1 beta by exposing specific binding sites, which are inaccessible in the native proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1990