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Biomedical subjects

M Renz

Publications and source records attributed to M Renz.

69 records · Page 4Linked to original sources
PubMed1980

Aggregation of small oligonucleosomal chains into 300-A globular particles.

Chicken erythrocyte oligonucleosomes (trimers to about 20-mers) are able to interact with each other through the very lysine-rich histones (H1 and H5) and form heterogeneous globular particles with a mean diameter of about 300 A. These particles assemble spontaneously during micrococcal nuclease digestion of chromatin in the presence of 30 mM NaCl and contain approximately 25 nucleosomes. They are sensitive to ionic strength and unfold at lower salt concentrations but can be reconstituted by restoring the initial salt concentration. Even at 30 mM NaCl, the particles remain dynamic structures, being in equilibrium with their oligonucleosomal components as revealed by the fact that particle stability depends on the concentration of oligonucleosomes.

Animals↗
PubMed1979

Heterogeneity of the chromosome fiber.

Evidence is presented that the 250 A thick chromosome fiber consists of clusters of nucleosomes (superbeads) which are heterogeneous in size. In bovine lymphocyte chromatin their number average corresponds to about 12 nucleosomes.

Animals↗
PubMed1979

Native and reconstituted chromosome fiber fragments.

The structure of hen erythrocyte chromatin fibers was studied with the electron microscope. Chromatin fiber fragments with a length of about 5,000 A and an average diameter of 320 A are composed of 13 globular subunits (superbeads) which contain different numbers of nucleosomes. Their number average corresponds to 17 nucleosomes. - The interaction of lysine-rich histones with nucleosome chains was investigated by reconstitution experiments and was found to be semi-cooperative.

Animals↗
PubMed1977

The chromosome fiber: evidence for an ordered superstructure of nucleosomes.

Chromosome fibers isolated from lymphocyte nuclei and prepared for electron microscopy by techniques designed to preserve their native structure have a distinctly knobby appearance, suggesting that DNA and protein are not distributed evenly along the fiber axis. Individual knobs (superbeads) are arranged in tandem and have an average diameter of about 200 A. Mild nuclease digestion of isolated nuclei releases apparent monomer superbeads that are composed of nucleohistone particles with the properties of nucleosomes. The kinetics of digestion indicate that the superbead is a discrete structural unit containing, on the average, about eight nucleosomes.

Animals↗
PubMed1977

Involvement of histone H1 in the organization of the chromosome fiber.

At high ionic strength (e.g., physiological salt concentrations) chromosome fibers are 200 A in diameter and composed of discrete globular structures that are held together by histone H1. At low ionic strength the fibers unfold and appear as the familiar chains of nucleosomes (80 A in diameter). The unfolding of chromosome fibers occurs within a narrow salt range. It results from a change in the mode of the interaction between histone H1 and the chromosome fiber and is very likely the consequence of a change from cooperative binding between histone H1 and DNA to a noncooperative binding. In the noncooperative binding state histone H1 molecules are randomly redistributed along the chromosome fiber.

Animals↗
PubMed1976

Transition from noncooperative to cooperative and selective binding of histone H1 to DNA.

A transition from noncooperative to cooperative binding of DNA and histone h1 occurs between 20 and 40mMNaCI in 5 mM Tris-HCI, pH 7.5. Below 20mM NaCI in mixtures in H1 and excess DNA, H1 binds to all of the DNA molecules, causing them to sediment faster, and does not distinguish between DNA molecules that differ in size or base composition. However, at NaCI concentrations above the narrow transition range, H1 binds to only some of the DNA molecules and leaves the rest free. If the DNA molecules in a mixture are the same size, H1 selectively binds those that have the highest content of adenosine (A)+thymidine (T). By means of competion experiments at salt concentrations spanning the transition range, it is demonstrated that H1 selectivity requires cooperativity. A high degree of selectivity based on A + T content can be produced by cooperative binding: for average DNA sizes of 2 X10(6) daltons, more than ten molecules of calf lymphocyte DNA (57% a+ t) are chosen per molecule of Escherichia coli DNA (50% A+T).

Adenosine↗
PubMed1975

Preferential and cooperative binding of histone I to chromosomal mammalian DNA.

There is a strong preferential binding of histone I to lymphocyte DNA as compared to Escherichia coli DNA when large DNA fragments (2 times 10-6 daltons) are used. The binding of histone I to lymphocyte DNA and to E. coli DNA is cooperative. The distribution of preferential binding sites has been investigated on fragmented DNA. Most of the 2 times 10-6 dalton fragments were found to have at least one preferential histone I binding site, whereas most of the 2 times 10-5 dalton fragments have none.

Animals↗
PubMedDate not supplied

Parameters predicting response to alpha-interferon treatment in chronic hepatitis C.

BACKGROUND/AIMS: Sustained response to alpha-interferon treatment for chronic hepatitis C is seen in only 25% of cases. Therefore, it is desirable to define pretreatment factors predicting responders. MATERIALS AND METHODS: Forty-nine patients with chronic hepatitis C were treated with a standard alpha-interferon regimen (3 x 3 MU s.c./week). Demographic, biochemical and immunological parameters, and HCV genotypes were obtained prior to initiation of treatment and evaluated for their value in predicting response to alpha-interferon therapy. RESULTS: Response, as defined by normalization of ALT, was 71% during interferon therapy and sustained response after discontinuation of interferon 24.5%. Patients infected with HCV-genotype 1b had significantly more often "community-acquired" disease. Their outcome was worse with a response rate of 44% during therapy and a sustained response of 12.5%, as compared to 87% and 27% respectively in patients infected with genotypes other than 1b. On multivariate analysis, absence of cirrhosis, HCV-genotype other than 1b, higher ALT levels and higher numbers of CD8 positive liver infiltrates were found to be predictors of response during alpha-interferon therapy. CONCLUSION: Response to alpha-interferon therapy seems to be influenced both by viral virulence factors and by the intensity of the host immune response to HCV.

Adult↗