THE VARIATION IN THE STRUCTURE OF ERYTHROCYTE NUCLEI WITH FIXATION

Observations have been made on the role of a divalent cation (calcium ion) during OsO4 fixation of nuclei of frog erythrocytes, mainly after isolation from cells. The volume of the nucleus depends partly on the molecular interaction of charged macromolecules, is controlled by the ionic strength of the medium, and hence may be used as a guide in attempts to preserve structure. When the isolation and fixation media contain 0.01 M calcium at pH 6.3 the volume changes, in the light microscope, during processing are small. When the fixative does not contain these ions, reversible volume changes occur during fixation and dehydration. The chromatin of nuclei processed with minimal volume change appears, in the electron microscope, to contain fine dots and lines about 20 to 40 A in diameter, relatively close together. The chromatin structure of nuclei in which volume changes have occurred consists of dense irregularly shaped patches, relatively far apart, and ranging in diameter from about 200 A down to the limits of visibility (20 to 30 A). It is suggested that the latter structure is a precipitation artefact.

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The ionic strength dependence of chromatin folding

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081966 ◽

1978 ◽

Vol 36 (2) ◽

pp. 220-221

Author(s):

F. Thoma ◽

TH. Koller

Keyword(s):

Electron Microscopy ◽

Electron Microscope ◽

Ionic Strength ◽

Specimen Preparation ◽

Preparation Technique ◽

Carbon Supports ◽

Ionic Strength Dependence ◽

Chromatin Folding ◽

Strength Dependence ◽

Preparation Techniques

Under a variety of electron microscope specimen preparation techniques different forms of chromatin appearance can be distinguished: beads-on-a-string, a 100 Å nucleofilament, a 250 Å fiber and a compact 300 to 500 Å fiber.Using a standardized specimen preparation technique we wanted to find out whether there is any relation between these different forms of chromatin or not. We show that with increasing ionic strength a chromatin fiber consisting of a row of nucleo- somes progressively folds up into a solenoid-like structure with a diameter of about 300 Å.For the preparation of chromatin for electron microscopy the avoidance of stretching artifacts during adsorption to the carbon supports is of utmost importance. The samples are fixed with 0.1% glutaraldehyde at 4°C for at least 12 hrs. The material was usually examined between 24 and 48 hrs after the onset of fixation.

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Faculty Opinions recommendation of The role of DNA methylation in setting up chromatin structure during development.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1013655.191567 ◽

2003 ◽

Author(s):

Frank Lyko

Keyword(s):

Dna Methylation ◽

Chromatin Structure

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A Role for Histone H2B During Repair of UV-Induced DNA Damage in Saccharomyces cerevisiae

Genetics ◽

10.1093/genetics/160.4.1375 ◽

2002 ◽

Vol 160 (4) ◽

pp. 1375-1387

Author(s):

Emmanuelle M D Martini ◽

Scott Keeney ◽

Mary Ann Osley

Keyword(s):

Dna Damage ◽

Dna Repair ◽

Chromatin Structure ◽

Specific Effect ◽

Cell Killing ◽

Cyclobutane Pyrimidine Dimers ◽

Histone H2b ◽

Uv Sensitivity ◽

Pyrimidine Dimers

Abstract To investigate the role of the nucleosome during repair of DNA damage in yeast, we screened for histone H2B mutants that were sensitive to UV irradiation. We have isolated a new mutant, htb1-3, that shows preferential sensitivity to UV-C. There is no detectable difference in bulk chromatin structure or in the number of UV-induced cis-syn cyclobutane pyrimidine dimers (CPD) between HTB1 and htb1-3 strains. These results suggest a specific effect of this histone H2B mutation in UV-induced DNA repair processes rather than a global effect on chromatin structure. We analyzed the UV sensitivity of double mutants that contained the htb1-3 mutation and mutations in genes from each of the three epistasis groups of RAD genes. The htb1-3 mutation enhanced UV-induced cell killing in rad1Δ and rad52Δ mutants but not in rad6Δ or rad18Δ mutants, which are defective in postreplicational DNA repair (PRR). When combined with other mutations that affect PRR, the histone mutation increased the UV sensitivity of strains with defects in either the error-prone (rev1Δ) or error-free (rad30Δ) branches of PRR, but did not enhance the UV sensitivity of a strain with a rad5Δ mutation. When combined with a ubc13Δ mutation, which is also epistatic with rad5Δ, the htb1-3 mutation enhanced UV-induced cell killing. These results suggest that histone H2B acts in a novel RAD5-dependent branch of PRR.

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Reaction mechanism of Ca2+-dependent adenosine triphosphatase of sarcoplasmic reticulum. ATP hydrolysis with CaATP as a substrate and role of divalent cation.

Journal of Biological Chemistry ◽

10.1016/s0021-9258(18)32113-6 ◽

1983 ◽

Vol 258 (14) ◽

pp. 8698-8707 ◽

Cited By ~ 21

Author(s):

M Shigekawa ◽

S Wakabayashi ◽

H Nakamura

Keyword(s):

Reaction Mechanism ◽

Sarcoplasmic Reticulum ◽

Divalent Cation ◽

Adenosine Triphosphatase ◽

Atp Hydrolysis

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Differential transcriptional regulation of the monocyte-chemoattractant protein-1 (MCP-1) gene in tumorigenic and non-tumorigenic HPV 18 positive cells: The role of the chromatin structure and AP-1 composition

Oncogene ◽

10.1038/sj.onc.1203643 ◽

2000 ◽

Vol 19 (29) ◽

pp. 3235-3244 ◽

Cited By ~ 33

Author(s):

Patrick Finzer ◽

Ubaldo Soto ◽

Hajo Delius ◽

Andrea Patzelt ◽

Johannes F Coy ◽

...

Keyword(s):

Transcriptional Regulation ◽

Chromatin Structure ◽

Monocyte Chemoattractant Protein 1 ◽

Monocyte Chemoattractant ◽

Monocyte Chemoattractant Protein ◽

Hpv 18

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Liver cell hydration and integrin signaling

Biological Chemistry ◽

10.1515/hsz-2021-0193 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Michele Bonus ◽

Dieter Häussinger ◽

Holger Gohlke

Keyword(s):

Cell Volume ◽

Liver Cell ◽

Cell Function ◽

The Other ◽

Signaling Cascades ◽

Integrin Signaling ◽

Volume Changes ◽

The One ◽

And Oxidative Stress

Abstract Liver cell hydration (cell volume) is dynamic and can change within minutes under the influence of hormones, nutrients, and oxidative stress. Such volume changes were identified as a novel and important modulator of cell function. It provides an early example for the interaction between a physical parameter (cell volume) on the one hand and metabolism, transport, and gene expression on the other. Such events involve mechanotransduction (osmosensing) which triggers signaling cascades towards liver function (osmosignaling). This article reviews our own work on this topic with emphasis on the role of β1 integrins as (osmo-)mechanosensors in the liver, but also on their role in bile acid signaling.

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