scholarly journals REPOPULATION OF THE POSTMITOTIC NUCLEOLUS BY PREFORMED RNA

1972 ◽  
Vol 53 (3) ◽  
pp. 611-623 ◽  
Author(s):  
Stephanie Gordon Phillips
Keyword(s):  
Actinomycin D ◽  
Chinese Hamster ◽  
Mitotic Cell ◽  
Fast Green ◽  
Azure B ◽  
Mouse Cells ◽  
Nucleolar Rna ◽  
L929 Mouse ◽  
Nucleolar Components ◽  
Mitotic Cells

This study is concerned with the fate of the nucleolar contents, particularly nucleolar RNA, during mitosis Mitotic cells harvested from monolayer cultures of Chinese hamster embryonal cells, KB6 (human) cells, or L929 (mouse) cells were allowed to proceed into interphase in the presence or absence (control) of 0.04–0 08 µg/ml of actinomycin D, a concentration which preferentially inhibits nucleolar (ribosomal) RNA synthesis 3 hr after mitosis, control cells had large, irregularly shaped nucleoli which stained intensely for RNA with azure B and for protein with fast green. In cells which had returned to interphase in the presence of actinomycin D, nucleoli were segregated into two components easily resolvable in the light microscope, and one of these components stained intensely for RNA with azure B. Both nucleolar components stained for protein with fast green In parallel experiments, cultures were incubated with 0.04–0 08 µg/ml actinomycin D for 3 hr before harvesting of mitotic cells, then mitotic cells were washed and allowed to return to interphase in the absence of actinomycin D. 3 hr after mitosis, nuclei of such cells were devoid of large RNA-containing structures, though small, refractile nucleolus-like bodies were observed by phase-contrast microscopy or in material stained for total protein. These experiments indicate that nucleolar RNA made several hours before mitosis persists in the mitotic cell and repopulates nucleoli when they reform after mitosis

scholarly journals NUCLEOLI OF DIPLOID CELL STRAINS

1971 ◽  
Vol 49 (3) ◽  
pp. 785-802 ◽  
Author(s):  
Stephanie G. Phillips ◽  
David M. Phillips
Keyword(s):  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Chinese Hamster ◽  
Diploid Cell ◽  
Particulate Material ◽  
Gradual Disappearance ◽  
Mouse Cells ◽  
Cell Strains ◽  
Nucleolar Components

Nucleoli of cultured Chinese hamster or mouse cells in early passages had a loosely reticular substructure. Within the reticulum small, irregularly shaped, light fibrillar zones occurred which were contiguous with denser fibrillar zones. These denser zones appeared to be connected in some places to the particulate material which composed the mass of the nucleolus. Generally, electron-transparent spaces separated the particulate zones from the fibrillar areas. Treatment with toyocamycin, an agent which is reported to cause a blockage in the processing of ribosomal RNA, greatly inhibited the accumulation of newly synthesized RNA in the cytoplasm, as monitored by radioautography. Toyocamycin treatment caused the gradual disappearance of the granules from the particulate region of the nucleoli, and resulted ultimately in the nucleoli appearing homogeneously fibrillar. Actinomycin D treatment, which inhibited virtually all RNA synthesis, caused a segregation, and finally a disaggregation, of nucleolar components.

scholarly journals REPOPULATION OF POSTMITOTIC NUCLEOLI BY PREFORMED RNA

1973 ◽  
Vol 58 (1) ◽  
pp. 54-63 ◽  
Author(s):  
David M. Phillips ◽  
Stephanie Gordon Phillips
Keyword(s):  
Electron Microscopy ◽  
Cell Cycle ◽  
Rna Synthesis ◽  
Actinomycin D ◽  
Normal Morphology ◽  
L929 Cells ◽  
Full Cell ◽  
Nucleolar Rna ◽  
Mitotic Cells

The reconstruction of the nucleolus after mitosis was analyzed by electron microscopy in cultured mammalian (L929) cells in which nucleolar RNA synthesis was inhibited for a 3 h period either after or before mitosis. When synchronized mitotic cells were plated into a concentration of actinomycin D sufficient to block nucleolar RNA synthesis preferentially, nucleoli were formed at telophase as usual. 3 h after mitosis, these nucleoli had fibrillar and particulate components and possessed the segregated appearance characteristic of nucleoli of actinomycin D-treated cells. Cells in which actinomycin D was present for the last 3 h preceding mitosis did not form nucleoli by 3 h after mitosis though small fibrillar prenucleolar bodies were detectable at this time. These bodies subsequently grew in size and eventually acquired a particulate component. It took about a full cell cycle before nucleoli of these cells were completely normal in appearance. Thus, nucleolar RNA synthesis after mitosis is not necessary for organization of nucleoli after mitosis. However, inhibition of nucleolar RNA synthesis before mitosis renders the cell incapable of forming nucleoli immediately after mitosis. If cells are permitted to resume RNA synthesis after mitosis, they eventually regain nucleoli of normal morphology.

scholarly journals THE EFFECT OF CRUDE PREPARATIONS OF VACCINIA ON MITOSIS AND DNA SYNTHESIS OF KB CELLS

1966 ◽  
Vol 124 (2) ◽  
pp. 199-208 ◽  
Author(s):  
Jadwiga Koziorowska ◽  
Krzysztof Włodarski
Keyword(s):  
Dna Synthesis ◽  
Mitotic Cell ◽  
Kb Cells ◽  
Cytologic Examination ◽  
Morphologic Study ◽  
One Stage ◽  
Cell Pool ◽  
Infected Cells ◽  
Mitotic Cells

A morphologic study has been made on KB cells infected with various doses of vaccinia as to DNA synthesis and mitosis. Determination of mitotic indices revealed that the mitotic cell pool depended on the proportion of infected cells and the time after infection. By cytologic examination neither mitotic lesions were found nor an accumulation of mitotic cells at any one stage of mitosis was demonstrated. Radioautographs of infected cultures have shown that the frequency of cells labeled over nuclei was significantly increased as compared with control cultures. Following the greatest dose of virus (multiplicity of 20 PFU/cell) the ratio of cells synthesizing DNA to mitotic cells increased from 45:5 at 5 hr to 50:0 at 50 hr. Concommittant with the appearance of this disparity between the DNA-synthesizing cell pool and mitotic cell pool the nuclei of cells became "lightly" labeled. Following the lowest dose of virus (multiplicity of 0.0002 PFU/cell) the increase of the fraction of mitotic cells was proportional to the increase of the fraction of cells which were labeled over nuclei.

scholarly journals Membrane traffic between secretory compartments is differentially affected during mitosis.

1990 ◽  
Vol 1 (5) ◽  
pp. 415-424 ◽  
Author(s):  
T Kreiner ◽  
H P Moore
Keyword(s):  
Plasma Membrane ◽  
Membrane Proteins ◽  
Secretory Pathway ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Membrane Traffic ◽  
Human Growth ◽  
Secretory Proteins ◽  
Viral Membrane ◽  
Mitotic Cells

Membrane traffic has been shown to be regulated during cell division. In particular, with the use of viral membrane proteins as markers, endoplasmic reticulum (ER)-to-Golgi transport in mitotic cells has been shown to be essentially blocked. However, the effect of mitosis on other steps in the secretory pathway is less clear, because an early block makes examination of following steps difficult. Here, we report studies on the functional characteristics of secretory pathways in mitotic mammalian tissue culture cells by the use of a variety of markers. Chinese hamster ovary cells were transfected with cDNAs encoding secretory proteins. Consistent with earlier results following viral membrane proteins, we found that the overall secretory pathway is nonfunctional in mitotic cells, and a major block to secretion is at the step between ER and Golgi: the overall rate of secretion of human growth hormone is reduced at least 10-fold in mitotic cells, and export of truncated vesicular stomatitis virus G protein from the ER is inhibited to about the same extent, as judged by acquisition of endoglycosidase H resistance. To ascertain the integrity of transport from the trans-Golgi to plasma membrane, we followed the secretion of sulfated glycosaminoglycan (GAG) chains, which are synthesized in the Golgi and thus are not subject to the earlier ER-to-Golgi block. GAG chains are valid markers for the pathway taken by constitutive secretory proteins; both protein secretion and GAG chain secretion are sensitive to treatment with n-ethyl-maleimide and monensin and are blocked at 19 degrees C. We found that the extent of GAG-chain secretion is not altered during mitosis, although the initial rate of secretion is reduced about twofold in mitotic compared with interphase cells. Thus, during mitosis, transport from the trans-Golgi to plasma membrane is much less hindered than ER-to-Golgi traffic. We conclude that transport steps are not affected to the same extent during mitosis.

Non-thermal effects of 2.45GHz microwaves on spindle assembly, mitotic cells and viability of Chinese hamster V-79 cells

2011 ◽  
Vol 716 (1-2) ◽  
pp. 1-9 ◽  
Author(s):  
Michela Ballardin ◽  
Ignazia Tusa ◽  
Nunzia Fontana ◽  
Agostino Monorchio ◽  
Chiara Pelletti ◽  
...  
Keyword(s):  
Thermal Effects ◽  
Chinese Hamster ◽  
Spindle Assembly ◽  
Mitotic Cells

scholarly journals Apical Constriction Reversal upon Mitotic Entry Underlies Different Morphogenetic Outcomes of Cell Division

2019 ◽  
Author(s):  
Clint S. Ko ◽  
Prateek Kalakuntla ◽  
Adam C. Martin
Keyword(s):  
Cell Division ◽  
Cell Shape ◽  
Mitotic Cell ◽  
Signal Interference ◽  
Apical Constriction ◽  
Mitotic Entry ◽  
Cell Divisions ◽  
Cell Shape Changes ◽  
Shape Changes ◽  
Mitotic Cells

AbstractDuring development, coordinated cell shape changes and cell divisions sculpt tissues. While these individual cell behaviors have been extensively studied, how cell shape changes and cell divisions that occur concurrently in epithelia influence tissue shape is less understood. We addressed this question in two contexts of the early Drosophila embryo: premature cell division during mesoderm invagination, and native ectodermal cell divisions with ectopic activation of apical contractility. Using quantitative live-cell imaging, we demonstrated that mitotic entry reverses apical contractility by interfering with medioapical RhoA signaling. While premature mitotic entry inhibits mesoderm invagination, which relies on apical constriction, mitotic entry in an artificially contractile ectoderm induced ectopic tissue invaginations. Ectopic invaginations resulted from medioapical myosin loss in neighboring mitotic cells. This myosin loss enabled non-mitotic cells to apically constrict through mitotic cell stretching. Thus, the spatial pattern of mitotic entry can differentially regulate tissue shape through signal interference between apical contractility and mitosis.

scholarly journals An asymmetric junctional mechanoresponse coordinates mitotic rounding with epithelial integrity

2021 ◽  
Vol 220 (5) ◽  
Author(s):  
Jooske L. Monster ◽  
Lisa Donker ◽  
Marjolein J. Vliem ◽  
Zaw Win ◽  
Helen K. Matthews ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Morphological Changes ◽  
Mitotic Cell ◽  
Cell Junctions ◽  
Actin Binding ◽  
Epithelial Barrier ◽  
Epithelial Integrity ◽  
Tensile Forces ◽  
Shape Changes ◽  
Mitotic Cells

Epithelia are continuously self-renewed, but how epithelial integrity is maintained during the morphological changes that cells undergo in mitosis is not well understood. Here, we show that as epithelial cells round up when they enter mitosis, they exert tensile forces on neighboring cells. We find that mitotic cell–cell junctions withstand these tensile forces through the mechanosensitive recruitment of the actin-binding protein vinculin to cadherin-based adhesions. Surprisingly, vinculin that is recruited to mitotic junctions originates selectively from the neighbors of mitotic cells, resulting in an asymmetric composition of cadherin junctions. Inhibition of junctional vinculin recruitment in neighbors of mitotic cells results in junctional breakage and weakened epithelial barrier. Conversely, the absence of vinculin from the cadherin complex in mitotic cells is necessary to successfully undergo mitotic rounding. Our data thus identify an asymmetric mechanoresponse at cadherin adhesions during mitosis, which is essential to maintain epithelial integrity while at the same time enable the shape changes of mitotic cells.

Correlation between resistance to actinomycin D, karyology, agglutination by concanavalin A and tumorigenicity in Chinese hamster hybrid cells

1975 ◽  
Vol 18 (1) ◽  
pp. 67-77
Author(s):  
I. Imbert ◽  
Y. Barra ◽  
M. Berebbi
Keyword(s):  
Statistical Analysis ◽  
Concanavalin A ◽  
Actinomycin D ◽  
Marker Chromosome ◽  
Chinese Hamster ◽  
Inverse Correlation ◽  
Sensitive Strain ◽  
Hybrid Cells ◽  
Hybrid Line

Subclones isolated from a Chinese hamster hybrid line, derived from fusion of an actinomycin D-resistant and an actinomycin D-sensitive strain, were studied with respect to their resistance to actinomycin D, karyology, transplantability and agglutination by concanavalin A. Statistical analysis of the results allowed the establishment of a classification of the strains based on increasing resistance to actinomycin D. There appeared to be an inverse correlation between actinomycin D-resistance and tumorigenicity and a positive correlation between this resistance and the presence of a marker chromosome.

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