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Biomedical subjects

B Puschendorf

Publications and source records attributed to B Puschendorf.

At least 163 records · Page 9Linked to original sources
PubMed1976

Subcellular distribution of histone-degrading enzyme activities from rat liver.

Chromatin prepared from liver tissue contains a histone-degrading enzyme activity with a pH optimum of 7.5-8.0, whereas chromatin isolated from purified nuclei is devoid of it. The histone-degrading enzyme activity was assayed with radioactively labelled total histones from Ehrlich ascites tumor cells. Among the different subcellular fractions assayed, only lysosomes and mitochondria exhibited histone-degrading enzymes. A pH optimum around 4.0-5.0 was found for the lysosomal fraction, whereas 7.5-8.0 has been found for mitochondria. Binding studies of frozen and thawed lysosomes or mitochondria to proteinase-free chromatin demonstrate that the proteinase associated with chromatin isolated from frozen tissue originates from damaged mitochondria. The protein degradation patterns obtained after acrylamide gel electrophoresis are similar for the chromatin-associated and the mitochondrial proteinase and different from that obtained after incubation with lysosomes. The chromatin-associated proteinase as well as the mitochondrial proteinase are strongly inhibited by 1.0 mM phenylmethanesulfonyl fluoride. Weak inhibition is found for lysosomal proteinases at pH 5. Kallikrein-trypsin inhibitor, however, inhibits lysosomal proteinase activity and has no effect on either chromatin-associated or mitochondrial proteinases. The higher template activity of chromatin isolated from a total homogenate compared to chromatin prepared from nuclei may be due to the presence of this histone-degrading enzyme activity.

Animals↗
PubMed1975

Macromolecular enzymatic product of NAD+ in liver mitochondria.

Rat liver mitochondria contain a Mg2+-requiring system that transfers the ADP-ribose moiety of NAD+ to an acceptor protein. The enzyme system was extracted in a soluble form and the ADP-ribosylated protein product was isolated by hydroxyapatite and Sephadex chromatography. The ADP-ribosylated protein product has a molecular weight of 100,000 and can be dissociated into subunits of 50,000 daltons by sodium dodecyl sulfate gel electrophoresis. Incubation of the isotopically labeled ADP-ribosylated protein with nicotinamide and a mitochondrial extract yields labeled NAD+, indicating apparent reversibility of the reaction. Enzymatic degradation of the ADP-ribosylated protein with snake venom phosphodiesterase liberates AMP and ADP-ribose or its isomer. Identification of these products and reversibility of the reaction show that the ADP-ribose moiety of NAD+ is the molecular species that is transferred to the acceptor protein. A fraction of the protein-bound ADP-ribose appears to be present as an an oligomer. The enzymatic protein-ADP-ribosylating reaction is inhibited by nicotinamide, ADP-ribose, the fluorophosphate of AMP, and picrylsulfonic acid.

Adenosine Diphosphate Sugars↗
PubMedDate not supplied

Glycogen phosphorylase isoenzyme BB in diagnosis of myocardial ischaemic injury and infarction.

This review deals with glycogen phosphorylase (GP) and its isoenzyme BB in the diagnosis of ischaemic myocardial injury. Early identification and confirmation of acute myocardial infarction is essential for correct patient care and disposition decision in the emergency department. In this respect, glycogen phosphorylase isoenzyme BB (GPBB) based on its metabolic function is an enzyme for early laboratory detection of ischaemia. In the aerobic heart muscle GPBB together with glycogen is tightly associated with the vesicles of the sarcoplasmic reticulum. Release of GPBB, the main isoform in the human myocardium, essentially depends on the degradation of glycogen, which is catalyzed by GP. Ischaemia is known to favour the conversion of bound GP in the b form into GP a, thereby accelerating glycogen breakdown, which is the ultimate prerequisite for getting GP into a soluble form being able to move freely in the cytosol. The efflux of GPBB into the extracellular fluid follows if ischaemia-induced structural alterations in the cell membrane become manifest. The clinical application of GPBB as a marker of ischaemic myocardial injury is a very promising tool for extending our knowledge of the severity of myocardial ischaemic events in the various coronary syndromes. The rational roots of this development were originated from Albert Wollenberger's research work on the biochemistry of cardiac ischaemia and the transient acceleration of glycogenolysis mainly brought about by GP activation.

Anaerobiosis↗
PubMedDate not supplied

Lack of correlation between histone H4 acetylation and transcription during the Physarum cell cycle.

The interaction between nucleosomal proteins and DNA is expected to change during DNA replication as well as during transcription. A possible way of achieving the necessary structural changes is the modification of histones and high mobility group (HMG) proteins. The acetylation of core histones has been studied in various systems (for a review see ref. 1) and a correlation between histone acetylation and transcriptional activity of chromatin has frequently been proposed. In particular, Bradbury and co-workers have reported a cell cycle dependence of histone H4 acetylation in Physarum polycephalum which revealed two correlations: (1) tetraacetylated H4 (H4Ac4) correlated with the rate of transcription and (2) H4 acetylation was inversely correlated with H1 phosphorylation in mitosis. We present evidence here that H4 acetylation does not fit these correlations. Our data clearly show that the acetate content of H4 is high during the S phase, but low during later stages of the cell cycle. H4Ac4 remains at a nearly constant level during the whole cycle, with an elevation during the S phase. Furthermore, experiments with the deacetylase inhibitor sodium-n-butyrate do not support the proposed connection between diacetylated H4 (H4Ac2) and DNA replication. Our data imply that a correlation of H4 acetylation and transcription is unlikely during the cell cycle of Physarum. The conclusions of Bradbury and co-workers are therefore invalid.

Acetylation↗