MARQUAGE A L'ARGENT AMMONIACAL DESCHROMOSOMES MITOTIQUES ET DES NOYAUX QUIESCENTS DE L'URODELE PLEURODELES WALTLII

1982 ◽  
Vol 24 (5) ◽  
pp. 541-548 ◽  
Author(s):  
Simone Bailly
Keyword(s):  
Cold Treatment ◽  
Silver Deposit ◽  
Mitotic Chromosomes ◽  
Interphase Nuclei ◽  
Pleurodeles Waltlii ◽  
Secondary Constrictions ◽  
Made In

Silver ammoniacal staining (Ag-As), specific for nuclear organizer regions (NORs) of mammals, has been applied to the interphase nuclei and to the mitotic chromosomes of the Triton Pleurodeles waltlii Michahelles. The banding on the chromosomes by the silver preferentially stains the pericentromeric zones where, after cold treatment, secondary constrictions appear. The metaphase karyotype (2n = 24) consists of two pairs of NORs which also stain with silver but to a lesser degree. It is also the same for the centromeres. This banding of zones other than those of the NORs is notable, not only in connection with the observations made in the case of the mammals, but also in connection with results obtained with other amphibians. An interpretation is given. The interphase nuclei also present sites of silver deposit. In the majority of cases, the sites correspond to the nucleoli. Nevertheless, supernumerary sites of deposit were apparent in a number of nuclei. This phenomenon cannot be explained clearly.[Translated by the journal]

scholarly journals Epichromatin is conserved in Toxoplasma gondii and labels the exterior parasite chromatin throughout the cell cycle

Parasitology ◽  
2013 ◽  
Vol 140 (9) ◽  
pp. 1104-1110 ◽  
Author(s):  
LAURA VANAGAS ◽  
MARIA C. DALMASSO ◽  
JEAN F. DUBREMETZ ◽  
ENRIQUE L. PORTIANSKY ◽  
DONALD E. OLINS ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Human Fibroblasts ◽  
Protozoan Parasite ◽  
Nuclear Fraction ◽  
Mitotic Chromosomes ◽  
Interphase Nuclei ◽  
The Face ◽  
Surface Covering ◽  
Intracellular Protozoan Parasite

SUMMARYToxoplasma gondii is an apicomplexan intracellular protozoan parasite responsible for toxoplasmosis, a disease with considerable medical and economic impact worldwide. Toxoplasma gondii cells never lose the nuclear envelope and their chromosomes do not condense. Here, we tested the murine monoclonal antibody PL2-6, which labels epichromatin (a conformational chromatin epitope based on histones H2A and H2B complexed with DNA), in T. gondii cultured in human fibroblasts. This epitope is present at the exterior chromatin surface of interphase nuclei and on the periphery of mitotic chromosomes in higher eukaryotes. PL2-6 reacted with T. gondii H2A and H2B histones in Western blot (WB) assays. In addition, the antibody reacted with the nuclear fraction of tachyzoites, as a single band coincident with H2B histone. In the T. gondii tachyzoite stage, PL2-6 also had peripheral nuclear localization, as observed by epifluorescence/confocal microscopy and immunoelectron microscopy. Confocal analysis showed that epichromatin is slightly polarized to one face of the parasite exterior chromatin surface. In replicating tachyzoites, PL2-6 also labels the exterior chromatin surface, covering the face of both segregating nuclei, facing the plasma membrane of the mother cell. The possible role of epichromatin in T. gondii is discussed.

scholarly journals THE STATE OF THE CHROMOSOMES IN THE INTERPHASE NUCLEUS

1949 ◽  
Vol 32 (4) ◽  
pp. 489-502 ◽  
Author(s):  
Hans Ris ◽  
A. E. Mirsky
Keyword(s):  
Interphase Nucleus ◽  
The State ◽  
Osmic Acid ◽  
Methyl Green ◽  
Extended State ◽  
Mitotic Chromosomes ◽  
Interphase Nuclei ◽  
Living Nucleus ◽  
Calf Thymus ◽  
Ordinary Light

In the living interphase nucleus no chromosomal structures are visible. Yet in the injured cell and after treatment with most histological fixatives chromatin structures become apparent. Under certain conditions this appearance of structure in the living interphase nucleus is reversible. We have found that this change in the interphase nucleus is the result of a change in the state of the chromosomes. In the living nucleus the chromosomes are in a greatly extended state, filling the entire nucleus. Upon injury the chromosomes condense and therefore become visible. At the same time the nuclear volume decreases. This behavior of the chromosomes is connected with their content of desoxyribonucleic acid (DNA). This view is based on the following observations: (a) Distribution of DNA in the Nucleus.—(1) The living interphase nucleus of uninjured cells absorbs diffusely at 2537 Å. No chromosomal structures are visible in ultraviolet photographs unless they are also distinct in ordinary light. If the chromosomes are made to condense they become visible and the absorption at 2537 Å is now localized in these structures. (2) After fixation with formalin and osmic acid interphase nuclei stain diffusely with Feulgen. These fixatives preserve the extended state of the chromosomes. (3) If nuclei are teased out in non-electrolytes (sucrose, glycerin) the chromosomes are extended. Such nuclei stain homogeneously with methyl green. On adding salts the chromosomes condense and the methyl green is now restricted to the visible structures. (b) Extension and Condensation of Isolated Chromosomes.—When chromosomes isolated from interphase nuclei of calf thymus are suspended in sucrose, their volume is four to five times larger than in saline, but they retain their characteristic shapes. Chromosomes from which DNA and histone have been removed do not show this reversible extension and condensation, neither do lampbrush chromosomes of frog oocytes which contain very little DNA. During mitosis a partial condensation of the DNA occurs in prophase, so that the mitotic chromosomes now occupy a much smaller volume of the nucleus. At telophase the chromosomes swell again to fill the entire nucleus.

Banding in mitotic chromosomes of Brassica campestris var. pekinensis with a trypsin–Giemsa method

Genome ◽  
1992 ◽  
Vol 35 (5) ◽  
pp. 899-901 ◽  
Author(s):  
Soryu Nishibayasahi
Keyword(s):  
Banding Pattern ◽  
Brassica Campestris ◽  
Chromosome Size ◽  
Mitotic Chromosomes ◽  
Metaphase Chromosomes ◽  
Secondary Constrictions

In Brassica campestris var. pekinensis cv. CR-strong, the karyotype comprised 12 median, 6 submedian, and 2 sub-terminal chromosomes. Secondary constrictions were observed in the two subterminal chromosomes. Banding pattern appeared very clearly in metaphase chromosomes with a trypsin–Giemsa method. It was possible to classify the chromosomes into 10 types (C1–C10), based on the chromosome size, shape, and banding pattern.Key words: Brassica campestris var. pekinensis, mitotic chromosomes, G-banding.

The Nucleolar Organizer in the Mitotic Chromosome Complement Of Xenopus Laevis

1962 ◽  
Vol s3-103 (64) ◽  
pp. 407-409
Author(s):  
J. KAHN
Keyword(s):  
Xenopus Laevis ◽  
Mitotic Chromosome ◽  
Chromosome Complement ◽  
Nucleolar Organizer ◽  
Interphase Nuclei ◽  
Nucleolar Number ◽  
Secondary Constrictions

The mutation which reduces nucleolar number in interphase nuclei of Xenopus laevisalso reduces the number of secondary constrictions in mitotic chromosome complements.

scholarly journals CENP-C Is Involved in Chromosome Segregation, Mitotic Checkpoint Function, and Kinetochore Assembly

2007 ◽  
Vol 18 (6) ◽  
pp. 2155-2168 ◽  
Author(s):  
Mi-Sun Kwon ◽  
Tetsuya Hori ◽  
Masahiro Okada ◽  
Tatsuo Fukagawa
Keyword(s):  
Mitotic Checkpoint ◽  
Conditional Knockout ◽  
Mitotic Chromosomes ◽  
Interphase Nuclei ◽  
Kinetochore Assembly ◽  
Checkpoint Pathway ◽  
Interphase Cells ◽  
Mitotic Delay ◽  
A Cell ◽  
Tetracycline Inducible System

CENP-C is a conserved inner kinetochore component. To understand the precise roles of CENP-C in the kinetochore, we created a cell line with a conditional knockout of CENP-C with the tetracycline-inducible system in which the target protein is inactivated at the level of transcription. We found that CENP-C inactivation causes mitotic delay. However, observations of living cells showed that CENP-C-knockout cells progressed to the next cell cycle without normal cell division after mitotic delay. Interphase cells with two nuclei before subsequent cell death were sometimes observed. We also found that ∼60% of CENP-C–deficient cells had no Mad2 signals even after treatment with nocodazole, suggesting that lack of CENP-C impairs the Mad2 spindle checkpoint pathway. We also observed significant reductions in the signal intensities of Mis12 complex proteins at centromeres in CENP-C–deficient cells. CENP-C signals were also weak in interphase nuclei but not in mitotic chromosomes of cells with a knockout of CENP-K, a member of CENP-H complex proteins. These results suggest that centromere localization of CENP-C in interphase nuclei occurs upstream of localization of the Mis12 complex and downstream of localization of the CENP-H complex.

scholarly journals Evidence for the organization of chromatin in megabase pair-sized loops arranged along a random walk path in the human G0/G1 interphase nucleus.

1995 ◽  
Vol 130 (6) ◽  
pp. 1239-1249 ◽  
Author(s):  
H Yokota ◽  
G van den Engh ◽  
J E Hearst ◽  
R K Sachs ◽  
B J Trask
Keyword(s):  
Random Walk ◽  
Dna Sequences ◽  
Large Scale ◽  
Loop Model ◽  
Interphase Nuclei ◽  
Attachment Sites ◽  
The Relationship ◽  
Made In ◽  
Random Walk Path

We determined the folding of chromosomes in interphase nuclei by measuring the distance between points on the same chromosome. Over 25,000 measurements were made in G0/G1 nuclei between DNA sequences separated by 0.15-190 megabase pairs (Mbp) on three human chromosomes. The DNA sequences were specifically labeled by fluorescence in situ hybridization. The relationship between mean-square interphase distance and genomic separation has two linear phases, with a transition at approximately 2 Mbp. This biphasic relationship indicates the existence of two organizational levels at scales > 100 kbp. On one level, chromatin appears to be arranged in large loops several Mbp in size. Within each loop, chromatin is randomly folded. On the second level, specific loop-attachment sites are arranged to form a supple, backbonelike structure, which also shows characteristic random walk behavior. This random walk/giant loop model is the simplest model that fully describes the observed large-scale spatial relationships. Additional evidence for large loops comes from measurements among probes in Xq28, where interphase distance increases and then locally decreases with increasing genomic separation.

scholarly journals RNA polymerase backtracking drives the accumulation of fission yeast condensin at active genes

2020 ◽  
Author(s):  
Julieta Rivosecchi ◽  
Laetitia Vachez ◽  
François Gautier ◽  
Pascal Bernard ◽  
Vincent Vanoosthuyse
Keyword(s):  
Rna Polymerase ◽  
Fission Yeast ◽  
Transcription Termination ◽  
Rna Polymerases ◽  
Mitotic Chromosomes ◽  
Dense Arrays ◽  
Made In ◽  
Active Genes

AbstractThe mechanisms leading to the accumulation of the SMC complex condensin around specific transcription units in mitosis remain unclear. Observations made in bacteria suggested that RNA polymerases (RNAP) constitute an obstacle to SMC translocation, particularly when RNAP and SMC travel in opposite directions. Whether this also applies to eukaryotic condensin remains unclear. Here we show in fission yeast that condensin remains focused at the 3’ end of an RNAP2-transcribed gene after flipping its orientation, suggesting that gene termini harbor intrinsic condensin-positioning features whatever the orientation of transcription. Consistent with this, we provide evidence that transcription termination mechanisms position condensin whatever the RNAP involved. Moreover, to stabilize backtracked RNAP2 polymerases within gene bodies was sufficient to cancel the accumulation of condensin at gene termini and to redistribute it evenly within transcription units. Altogether, our results suggest that RNAP backtracking, which is frequent at gene termini, plays a key role in positioning condensin and strengthen the idea that dense arrays of proteins tightly-bound to DNA alter the distribution of condensin on mitotic chromosomes.

scholarly journals Chromosome number and secondary constriction variation in 51 accessions of a citrus germplasm bank

1997 ◽  
Vol 20 (3) ◽  
pp. 489-496 ◽  
Author(s):  
Marcelo Guerra ◽  
Andrea Pedrosa ◽  
Ana Emília Barros e Silva ◽  
Maria Tereza Marquim Cornélio ◽  
Karla Santos ◽  
...  
Keyword(s):  
Secondary Constriction ◽  
Chromatin Condensation ◽  
Proximal Region ◽  
Citrus Species ◽  
Germplasm Bank ◽  
Mitotic Chromosomes ◽  
Citrus Germplasm ◽  
Numerical Variation ◽  
Subterminal Region ◽  
Secondary Constrictions

The mitotic chromosomes of 51 citrus accessions from the Centro Nacional de Pesquisa em Mandioca e Fruticultura Tropical, Cruz das Almas, BA, Brazil, were analyzed. The sample included representatives of 20 Citrus species, one of Poncirus and seven hybrids. All accessions showed 2n = 18 without any evidence of numerical variation. The most clearly variable karyotype feature was the number and position of secondary constrictions (SECs). In 19 accessions the SECs were not identified, mainly due to the degree of chromatin condensation. In the remainder they varied in number from one to three per karyotype. They were found in the proximal region of one of the three largest chromosome pairs, in the terminal/subterminal region of a smaller chromosome or, more seldom, terminally in a larger chromosome. Only in a few cases were such constrictions observed simultaneously in both homologues of the same chromosome pair. The high variability of this karyotype feature may be due to the activation of this region in the previous interphase but may also indicate a high structural variability and heterozygosity of citrus germplasms

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