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H Sieber

Publications and source records attributed to H Sieber.

7 recordsLinked to original sources
PubMed2005

Classification of abnormal fundus autofluorescence patterns in the junctional zone of geographic atrophy in patients with age related macular degeneration.

AIM: To describe and classify patterns of abnormal fundus autofluorescence (FAF) in the junctional zone of geographic atrophy (GA) in patients with age related macular degeneration. METHODS: Digital FAF images were recorded in 164 eyes of 107 patients using a confocal scanning laser ophthalmoscope (cSLO; excitation 488 nm, detection above 500 nm) as part of a prospective multicentre natural history study (FAM Study). FAF images were obtained in accordance with a standardised protocol for digital image acquisition and generation of mean images after automated alignment. RESULTS: Image quality was sufficient for classification of FAF patterns in 149 eyes (90.9%) with lens opacities being the most common reason for insufficient image quality. Abnormal FAF outside GA in 149 eyes was classified into four patterns: focal (12.1%), banded (12.8%), patchy (2.0%), and diffuse (57.0%), whereby 12.1% had normal background FAF in the junctional zone. In 4% there was no predominant pattern. The diffuse pattern was subdivided into four groups including reticular (4.7%), branching (27.5%), fine granular (18.1%), and fine granular with peripheral punctate spots (6.7%). CONCLUSIONS: Different phenotypic patterns of abnormal FAF in the junctional zone of GA can be identified with cSLO FAF imaging. These distinct patterns may reflect heterogeneity at a cellular and molecular level in contrast with a non-specific ageing process. A refined phenotypic classification may be helpful to identify prognostic determinants for the spread of atrophy and visual loss, for identification of genetic risk factors as well as for the design of future interventional trials.

Aged↗
PubMed2001

PIASy, a nuclear matrix-associated SUMO E3 ligase, represses LEF1 activity by sequestration into nuclear bodies.

The Wnt-responsive transcription factor LEF1 can activate transcription in association with beta-catenin and repress transcription in association with Groucho. In search of additional regulatory mechanisms of LEF1 function, we identified the protein inhibitor of activated STAT, PIASy, as a novel interaction partner of LEF1. Coexpression of PIASy with LEF1 results in potent repression of LEF1 activity and in covalent modification of LEF1 with SUMO. PIASy markedly stimulates the sumoylation of LEF1 and multiple other proteins in vivo and functions as a SUMO E3 ligase for LEF1 in a reconstituted system in vitro. Moreover, PIASy binds to nuclear matrix-associated DNA sequences and targets LEF1 to nuclear bodies, suggesting that PIASy-mediated subnuclear sequestration accounts for the repression of LEF1 activity.

Animals↗
PubMed1986

Highly selective affinity labelling of RNA polymerase B (II) from wheat germ.

DNA-dependent RNA polymerase B (II) from wheat germ was modified by incubation with 4-[N-(beta-hydroxyethyl)-N-methyl]benzaldehyde esters of AMP, ADP or ATP, followed by reduction with NaBH4. Reaction of the modified enzyme with [alpha-32P]UTP in the presence of various DNA templates led to a highly selective affinity labelling of the subunit with Mr 140 000 by covalently linked ApU. Labelling was inhibited by 1 microgram/ml alpha-amanitin.

Affinity Labels↗
PubMed1985

Primer-independent abortive initiation by wheat-germ RNA polymerase B (II).

Highly purified RNA polymerase B (II) from wheat germ catalyses the formation of dinucleoside tetraphosphates from ribonucleoside triphosphates in the absence of an oligonucleotide primer or additional protein factors. The reaction requires bivalent cations such as Mn2+ or Mg2+ and proceeds linearly for several hours. It is strongly inhibited by 1 microgram/ml alpha-amanitin or 2 micrograms/ml heparin. The reaction strictly depends on the addition of a specific linear or circular DNA template, such as the plasmid pSmaF or a DNA fragment containing the gene for nopaline dehydrogenase. Bacteriophage T7 D111 DNA has almost no template activity. The start sites for dinucleotide synthesis on the template are limited. With the DNA fragment containing the gene for nopaline dehydrogenase only pppApA and pppApU are synthesised substantially whereas pppUpU is formed only in trace amounts. No significant dinucleotide synthesis is observed with other ribonucleoside triphosphates either singly or in a combination of two. The various regions of the DNA fragment differ distinctly in template activity.

Catalysis↗