Electron-Microscope Observations on the Structure of Condensed Chromatin: Evidence for Orderly Arrays of Unit Threads on the Surface of Chicken Erythrocyte Nuclei

1970 ◽  
Vol 7 (1) ◽  
pp. 35-48
Author(s):  
A. C. EVERID ◽  
J. V. SMALL ◽  
H. G. DAVIES
Keyword(s):  
Nuclear Envelope ◽  
Sodium Citrate ◽  
Condensed Chromatin ◽  
Chicken Erythrocyte ◽  
Cell Nuclei ◽  
Structural Element ◽  
Thin Sections ◽  
Small Areas ◽  
The Common ◽  
Degree Of Order

A unit thread has been identified by electron microscopy as the common structural element in the condensed chromatin of a variety of cell nuclei. From the previous studies of thin sections normal to the nuclear envelope it was concluded that the unit thread, of diameter about 17 nm but varying somewhat depending on fixation, packed with spacings of about 28 nm on the surface of the nucleus to form one or more layers. Thin sections tangential to the nuclear envelope, described in this paper, reveal directly the degree of order within the surface layer; there are small areas or patches in which the units are regularly arranged. Units are also orderly arranged around the pores in the nuclear envelope. Unit threads are less easily visible in electron micrographs of mature erythrocytes than at earlier stages of development but the clarity with which they can be seen is increased by a brief treatment prior to fixation with sodium citrate.

scholarly journals Stereo electron microscopy of the 25-nm chromatin fibers in isolated nuclei.

1979 ◽  
Vol 81 (1) ◽  
pp. 260-265 ◽  
Author(s):  
A L Olins ◽  
D E Olins
Keyword(s):  
Electron Microscopy ◽  
Nuclear Envelope ◽  
Electron Micrographs ◽  
Chicken Erythrocyte ◽  
Thin Sections ◽  
Isolated Nuclei ◽  
Chromatin Fibers

Thin sections (0.1-0.25 micron) of isolated chicken erythrocyte nuclei were examined at various tilt angles. Stereo pairs of electron micrographs document the parallel alignment of 25-nm chromatin fibers adjacent to the nuclear envelope, and demonstrate a fiber substructure consistent with close-packed arrays of nucleosomes.

Electron-microscope observations on cell nuclei in various tissues of a teleost fish: the nucleolus-associated monolayer of chromatin structural units

1976 ◽  
Vol 21 (2) ◽  
pp. 315-327
Author(s):  
H.G. Davies ◽  
M.E. Haynes
Keyword(s):  
Electron Microscope ◽  
Connective Tissue ◽  
Nuclear Envelope ◽  
Teleost Fish ◽  
Base Sequence ◽  
Cell Nuclei ◽  
Structural Units ◽  
Thin Sections ◽  
Chromatin Structural ◽  
In Cells

Observations on stain uptake by thin sections through condensed interphase chromosomes in cells from epithelial and muscle tissue in kidney and intestine, and also in fibroblasts, show a distribution into DNA-rich and DNA-poor phases similar to that already described in cells from the connective tissue blood. In all the nuclei the nucleolus, when adjacent to the nuclear envelope, is separated from the inner membrane by a monolayer of chromatin structural units, similar to the monolayer enclosed on both sides by nuclear envelope, previously described in a wide variety of organisms. The data provide further support for the hypothesis that the condensed interphase chromosomes in eukaryotes are characterized by essentially similar structural units folded to form similar patterns. This hypothesis, regarding the higher order units, is consistent with data of others which show that histones and DNA fold to form similar repeating subunits in chromatin, irrespective of the base sequence in the DNA and the origin of the histones.

The Ultrastructure of the Nuclear Events of Binary Fission in Paramecium bursaria and the Effects of Colchicine on Cell Division

1974 ◽  
Vol 32 ◽  
pp. 276-277
Author(s):  
L. M. Lewis
Keyword(s):  
Cell Division ◽  
Nuclear Envelope ◽  
Condensed Chromatin ◽  
Binary Fission ◽  
Paramecium Bursaria ◽  
Nuclear Events ◽  
Division Axis

The effects of colchicine on extranuclear microtubules associated with the macronucleus of Paramecium bursaria were studied to determine the possible role that these microtubules play in controlling the shape of the macronucleus. In the course of this study, the ultrastructure of the nuclear events of binary fission in control cells was also studied.During interphase in control cells, the micronucleus contains randomly distributed clumps of condensed chromatin and microtubular fragments. Throughout mitosis the nuclear envelope remains intact. During micronuclear prophase, cup-shaped microfilamentous structures appear that are filled with condensing chromatin. Microtubules are also present and are parallel to the division axis.

Membranous alterations in the cytoplasm and nucleus in a primitive neuroectodermal tumor of the brain

1978 ◽  
Vol 36 (2) ◽  
pp. 628-629
Author(s):  
C. N. Sun ◽  
C. Araoz ◽  
H. J. White
Keyword(s):  
Nuclear Envelope ◽  
Tumor Cells ◽  
Osmium Tetroxide ◽  
Primitive Neuroectodermal Tumor ◽  
Uranyl Acetate ◽  
Neuroectodermal Tumor ◽  
Annulate Lamellae ◽  
Lead Citrate ◽  
Thin Sections ◽  
The Brain

The ultrastructure of a cerebral primitive neuroectodermal tumor has been reported previously. In the present case, we will present some unusual previously unreported membranous structures and alterations in the cytoplasm and nucleus of the tumor cells.Specimens were cut into small pieces about 1 mm3 and immediately fixed in 4% glutaraldehyde in phosphate buffer for two hours, then post-fixed in 1% buffered osmium tetroxide for one hour. After dehydration, tissues were embedded in Epon 812. Thin sections were stained with uranyl acetate and lead citrate.In the cytoplasm of the tumor cells, we found paired cisternae (Fig. 1) and annulate lamellae (Fig. 2) noting that the annulate lamellae were sometimes associated with the outer nuclear envelope (Fig. 3). These membranous structures have been reported in other tumor cells. In our case, mitochondrial to nuclear envelope fusions were often noted (Fig. 4). Although this phenomenon was reported in an oncocytoma, their frequency in the present study is quite striking.

Automated Cell Nuclei Segmentation on Cervical Smear Images Using Structure Analysis

2021 ◽  
Vol 51 ◽  
pp. 105-115
Author(s):  
Wan Azani Mustafa ◽  
Low Zhe Wei ◽  
Khairul Shakir Ab Rahman
Keyword(s):  
Cervical Cancer ◽  
Pap Smear ◽  
Standard Technique ◽  
Successful Implementation ◽  
Cell Nuclei ◽  
Structural Element ◽  
Detection Techniques ◽  
Nuclei Segmentation ◽  
Common Cancer ◽  
Early Century

Cervical cancer is a common cancer that affects women around the world, and it is also the most common cancer in the developing countries. The cancer burden has increased due to several factors, such as population growth and ageing. In the early century, the systematization of cervical cancer cells takes some time to process manually, and the result that comes out is also inaccurate. This article presents a new nucleus segmentation on pap smear cell images based on structured analysis or morphological approach. Morphology is a broad set of image processing operations that process images based on shape, size and structure. This operation applies a structural element of the image to create an output image of the same size. The most basic of these operations are dilation and erosion. The results of the numerical analysis indicate that the proposed method achieved about 94.38% (sensitivity), 82.56% (specificity) and 93% (accuracy). Also, the resulting performance was compared to a few existing techniques such as Bradley Method, Nick Method and Sauvola Method. The results presented here may facilitate improvements in the detection method of the pap smear cell image to resolve the time-consuming issue and support better system performance to prevent low precision result of the Human Papilloma Virus (HPV) stages. The main impact of this paper is will help the doctor to identify the patient disease based on Pap smear analysis such as cervical cancer and increase the percentages of accuracy compared to the conventional method. Successful implementation of the nucleus detection techniques on Pap smear image can become a standard technique for the diagnosis of various microbiological infections such as Malaria and Tuberculosis.

Nuclear envelope removal/maintenance determines the structural and functional remodelling of embryonic red blood cell nuclei in activated mouse oocytes

Zygote ◽  
1998 ◽  
Vol 6 (1) ◽  
pp. 65-73 ◽  
Author(s):  
Daniel Szöllösi ◽  
Renata Czołowska ◽  
Ewa Borsuk ◽  
Maria S. Szöllösi ◽  
Pascale Debey
Keyword(s):  
Nuclear Envelope ◽  
Transcriptional Activity ◽  
Chromatin Condensation ◽  
Oocyte Activation ◽  
Cell Nuclei ◽  
Nuclear Envelope Breakdown ◽  
Mouse Oocytes ◽  
Female Pronucleus ◽  
Mouse Fetuses

SummaryNuclei of embryonic red blood cells (e-RBC) from 12-day mouse fetuses are arrested in Go phase of the cell cycle and have low transcriptional activity. These nuclei were transferred with help of polyethylene glycol (PEG)-mediated fusion to parthenogenetically activated mouse oocytes and heterokaryons were analysed for nuclear structure and transcriptional activity. If fusion proceeded 25–45 min after oocyte activation, e-RBC nuclei were induced to nuclear envelope breakdown and partial chromatin condensation, followed by formation of nuclei structurally identical with pronuclei. These ‘pronuclei’, similar to egg (female) pronuclei, remained transcriptionally silent over several hours of in vitro culture. If fusion was performed 1 h or later (up to 7 h) after activation, the nuclear envelope of e-RBC nuclei remained intact and nuclear remodelling was less spectacular (slight chromatin decondensation, formation of nucleolus precursor bodies). These nuclei, however, reinforced polymerase-II-dependent transcription within a few hours of in vitro culture. Our present experiments, together with our previous work, demonstrate that nuclear envelope breakdown/maintenance are critical events for nuclear remodelling in activated mouse oocytes and that somatic dormant nuclei can be stimulated to renew transcription at a time when the female pronucleus remains transcriptionally silent.

scholarly journals Morphological and morphometric changes of bone tissue in patients with osteoporosis and osteomalation

TRAUMA ◽  
2021 ◽  
Vol 22 (5) ◽  
pp. 9-14
Author(s):  
O.M. Ignatiev ◽  
M.I. Turchyn ◽  
V.A. Ulianov ◽  
T.A. Yermolenko
Keyword(s):  
Bone Tissue ◽  
Working Conditions ◽  
Functional Activity ◽  
Morphological Changes ◽  
Differential Staining ◽  
Cell Nuclei ◽  
Mineral Density ◽  
Common Features ◽  
Diagnostic Measures ◽  
The Common

Bone tissue was studied in 56 postmenopausal women (mean age 62.30 ± 2.74 years), of which 46 patients who worked in unfavorable working conditions had a decreased bone mineral density (BMD) (osteoporosis (OP) — in 31 women, osteomalacia (OM) — in 13); 10 women had no metabolic changes in bone tissue (BT). A BT scan fragment was obtained during surgery for a fracture of the femoral neck. Non-decalcified QD sections were prepared, the functional activity of the QD cell nuclei was determined using the method of differential staining of nuclei with different functional activity. Morphological changes in OP and OM have both common features and differences. The common is the thinning of the bone rods, the expansion of the canals of osteons, the presence of cell-free areas, and cell-free lacunae. In contrast to OP, OM presents with the thickness and area of the osteoid increase, a less pronounced decrease in oxyphyllin matrix, a higher functional activity of BT cells. A decrease in BMD and the occurrence of low-energy fractures may result not only from OP but also OM. When prescribing treatment, it is necessary to carry out diffe-rential diagnostic measures that determine the cause of the decrease in bone mass.

scholarly journals DNA Replication in Quiescent Cell Nuclei: Regulation by the Nuclear Envelope and Chromatin Structure

1999 ◽  
Vol 10 (12) ◽  
pp. 4091-4106 ◽  
Author(s):  
Zhi Hong Lu ◽  
Hongzhi Xu ◽  
Gregory H. Leno
Keyword(s):  
Dna Replication ◽  
Nuclear Envelope ◽  
Chromatin Structure ◽  
Cell Nuclei ◽  
Free System ◽  
Replication Complex ◽  
Linker Histones ◽  
Egg Extract ◽  
Initiation Of Replication ◽  
Stable Association

Quiescent nuclei from differentiated somatic cells can reacquire pluripotence, the capacity to replicate, and reinitiate a program of differentiation after transplantation into amphibian eggs. The replication of quiescent nuclei is recapitulated in extracts derived from activated Xenopus eggs; therefore, we have exploited this cell-free system to explore the mechanisms that regulate initiation of replication in nuclei from terminally differentiatedXenopus erythrocytes. We find that these nuclei lack many, if not all, pre-replication complex (pre-RC) proteins. Pre-RC proteins from the extract form a stable association with the chromatin of permeable nuclei, which replicate in this system, but not with the chromatin of intact nuclei, which do not replicate, even though these proteins cross an intact nuclear envelope. During extract incubation, the linker histones H1 and H10 are removed from erythrocyte chromatin by nucleoplasmin. We show that H1 removal facilitates the replication of permeable nuclei by increasing the frequency of initiation most likely by promoting the assembly of pre-RCs on chromatin. These data indicate that initiation in erythrocyte nuclei requires the acquisition of pre-RC proteins from egg extract and that pre-RC assembly requires the loss of nuclear envelope integrity and is facilitated by the removal of linker histone H1 from chromatin.

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