scholarly journals Control mechanisms af cell division and radiation

1969 ◽  
Vol 9 (1) ◽  
pp. 21-33
Author(s):  
Yukio DOIDA
Keyword(s):  
Cell Division ◽  
Control Mechanisms

scholarly journals Dissecting the Control Mechanisms for DNA Replication and Cell Division in E. coli

Cell Reports ◽  
2018 ◽  
Vol 25 (3) ◽  
pp. 761-771.e4 ◽  
Author(s):  
Gabriele Micali ◽  
Jacopo Grilli ◽  
Jacopo Marchi ◽  
Matteo Osella ◽  
Marco Cosentino Lagomarsino
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Control Mechanisms ◽  
E Coli

scholarly journals Towards an understanding of spiral patterning in the Sargassum muticum shoot apex

2017 ◽  
Author(s):  
Marina Linardić ◽  
Siobhan A. Braybrook
Keyword(s):  
Cell Division ◽  
Brown Alga ◽  
Apical Meristem ◽  
Apical Cell ◽  
The Body ◽  
Sargassum Muticum ◽  
Control Mechanisms ◽  
Lateral Organs ◽  
Division Pattern ◽  
Underlying Mechanisms

AbstractIn plants and parenchymatous brown algae the body arises through the activity of an apical meristem (a niche of cells or a single cell). The meristem produces lateral organs in specific patterns, referred to as phyllotaxis. In plants, two different control mechanisms have been proposed – one is position-dependent and relies on morphogen accumulation at future organ sites whereas the other is a lineage-based system which links phyllotaxis to the apical cell division pattern. Here we examine the apical patterning of the brown alga, Sargassum muticum, which exhibits spiral phyllotaxis (137.5° angle) and an unlinked apical cell division pattern. The Sargassum apex presents characteristics of a self-organising system, similar to plant meristems. We were unable to correlate the plant morphogen auxin with bud positioning in Sargassum, nor could we predict cell wall softening at new bud sites. Our data suggests that in Sargassum muticum there is no connection between phyllotaxis and the apical cell division pattern indicating a position-dependent patterning mechanism may be in place. The underlying mechanisms behind the phyllotactic patterning appear to be distinct from those seen in plants.SummaryThe brown alga Sargassum muticum displays spiral phyllotaxis developed from a position-dependent self-organising mechanism, different from that understood in plants.

scholarly journals The Pneumococcal Divisome: Dynamic Control of Streptococcus pneumoniae Cell Division

2021 ◽  
Vol 12 ◽  
Author(s):  
Nicholas S. Briggs ◽  
Kevin E. Bruce ◽  
Souvik Naskar ◽  
Malcolm E. Winkler ◽  
David I. Roper
Keyword(s):  
Cell Wall ◽  
Cell Division ◽  
Streptococcus Pneumoniae ◽  
Virulence Factors ◽  
Protein Complexes ◽  
Dynamic Control ◽  
Capsular Polysaccharides ◽  
Control Mechanisms ◽  
Cell Wall Synthesis ◽  
Molecular Events

Cell division in Streptococcus pneumoniae (pneumococcus) is performed and regulated by a protein complex consisting of at least 14 different protein elements; known as the divisome. Recent findings have advanced our understanding of the molecular events surrounding this process and have provided new understanding of the mechanisms that occur during the division of pneumococcus. This review will provide an overview of the key protein complexes and how they are involved in cell division. We will discuss the interaction of proteins in the divisome complex that underpin the control mechanisms for cell division and cell wall synthesis and remodelling that are required in S. pneumoniae, including the involvement of virulence factors and capsular polysaccharides.

scholarly journals Microinjection of the catalytic fragment of myosin light chain kinase into dividing cells: effects on mitosis and cytokinesis.

1991 ◽  
Vol 114 (5) ◽  
pp. 967-975 ◽  
Author(s):  
D J Fishkind ◽  
L G Cao ◽  
Y L Wang
Keyword(s):  
Cell Division ◽  
Light Chain ◽  
Myosin Light Chain Kinase ◽  
Myosin Light Chain ◽  
Contractile Activity ◽  
Cell Cortex ◽  
Control Mechanisms ◽  
Nuclear Envelope Breakdown ◽  
Dividing Cells ◽  
Catalytic Fragment

Myosin light chain kinase (MLCK) is thought to regulate the contractile activity in smooth and non-muscle cells, and may play an important role in controlling the reorganization of the actin-myosin cytoskeleton during cell division. To test this hypothesis we have microinjected the 61-kD catalytic fragment of MLCK into mitotic cells, and examined the effects of unregulated MLCK activity on cell division. The microinjection of active 61 kD causes both a significant delay in the transit time from nuclear envelope breakdown to anaphase onset, and an increase in motile surface activity during and after metaphase. Control experiments with intact MLCK or with inactive catalytic fragment suggest that these effects are specifically induced by the unregulated myosin light chain kinase activity. Immunofluorescence analysis suggests that delays in mitosis are coupled to disruptions of spindle structures, while increased surface motility may be related to changes in the organization of actin and myosin at the cell cortex. Most importantly, despite the expression of strong phenotypes, 61 kD-injected cells still form functional cleavage furrows that progress through cytokinesis at rates identical to those of control cells. Together, these results suggest that the activity of MLCK can affect mitosis and cortical activities, however additional control mechanisms are likely involved in the regulation of cytokinesis.

scholarly journals Concentration fluctuations due to size-dependent gene expression and cell-size control mechanisms

2021 ◽  
Author(s):  
Chen Jia ◽  
Abhyudai Singh ◽  
Ramon Grima
Keyword(s):  
Gene Expression ◽  
Cell Division ◽  
Cell Size ◽  
Gene Dosage ◽  
Size Control ◽  
Reaction Rates ◽  
Concentration Fluctuations ◽  
Cycle Phase ◽  
Control Mechanisms ◽  
Size Dependent

Intracellular reaction rates depend on concentrations and hence their levels are often regulated. However classical models of stochastic gene expression lack a cell size description and cannot be used to predict noise in concentrations. Here, we construct a model of gene product dynamics that includes a description of cell growth, cell division, size-dependent gene expression, gene dosage compensation, and size control mechanisms that can vary with the cell cycle phase. We obtain expressions for the approximate distributions and power spectra of concentration fluctuations which lead to insight into the emergence of concentration homeostasis. Furthermore, we find that (i) the conditions necessary to suppress cell division-induced concentration oscillations are difficult to achieve; (ii) mRNA concentration and number distributions can have different number of modes; (iii) certain size control strategies are ideal because they maintain constant mean concentrations whilst minimising concentration noise. Predictions are confirmed using lineage data for E. coli, fission yeast and budding yeast.

scholarly journals Dissecting the control mechanisms for DNA replication and cell division in E. coli

2018 ◽  
Author(s):  
Gabriele Micali ◽  
Jacopo Grilli ◽  
Jacopo Marchi ◽  
Matteo Osella ◽  
Marco Cosentino Lagomarsino
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Genome Replication ◽  
Control Mechanisms ◽  
Cycle Progression ◽  
E Coli ◽  
Classic Problem ◽  
Initiation Of Replication ◽  
Initiation Of Dna Replication

Understanding how single E. coli cells coordinate the timing of cell division with genome replication would unlock a classic problem of biology, and open the way to address cell-cycle progression at the single-cell level. Several recent studies produced new data and proposed different models, based on the hypothesis that replication-segregation is the bottleneck process for cell division. However, due to the apparent contrast in both experimental results and proposed mechanisms, the emerging picture is fragmented and unclear. In this work, we re-evaluate jointly available data and models, and we show that, while each model contains useful insights, none of the proposed models, as well as generalizations based on the same assumptions, correctly describes all the correlation patterns observed in data. This analysis leads us to conclude that the assumption that replication is the bottleneck process for cell division is too restrictive. Instead, we propose that two concurrent cycles responsible for division and initiation of DNA replication together set the time of cell division. This framework correctly captures available data and allows us to select a nearly constant added size per origin between subsequent initiations as the most likely mechanism setting initiation of replication.

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.

Stimulated Virus Production in Vinblastine and Cytochalasin-Induced Multinucleate Cells

1970 ◽  
Vol 28 ◽  
pp. 186-187
Author(s):  
Krishan Awtar
Keyword(s):  
Cell Division ◽  
Normal Cell ◽  
Virus Production ◽  
Multinucleate Cells ◽  
Daughter Cells ◽  
Cell Divisions ◽  
Nuclear Membranes ◽  
Division 2 ◽  
Vinblastine Sulfate

Exposure of cells to low sublethal but mitosis-arresting doses of vinblastine sulfate (Velban) results in the initial arrest of cells in mitosis followed by their subsequent return to an “interphase“-like stage. A large number of these cells reform their nuclear membranes and form large multimicronucleated cells, some containing as many as 25 or more micronuclei (1). Formation of large multinucleate cells is also caused by cytochalasin, by causing the fusion of daughter cells at the end of an otherwise .normal cell division (2). By the repetition of this process through subsequent cell divisions, large cells with 6 or more nuclei are formed.

Confocal microscopy of the cytoskeleton in living plant cells following microinjection of fluorescent probes

1993 ◽  
Vol 51 ◽  
pp. 130-131
Author(s):  
Ann Cleary
Keyword(s):  
Cell Division ◽  
Fluorescent Probes ◽  
Actin Filaments ◽  
Intracellular Transport ◽  
Cell Structure ◽  
Plant Cells ◽  
Cell Plate ◽  
Cell Cortex ◽  
Living Plant ◽  
Rhodamine Phalloidin

Microinjection of fluorescent probes into living plant cells reveals new aspects of cell structure and function. Microtubules and actin filaments are dynamic components of the cytoskeleton and are involved in cell growth, division and intracellular transport. To date, cytoskeletal probes used in microinjection studies have included rhodamine-phalloidin for labelling actin filaments and fluorescently labelled animal tubulin for incorporation into microtubules. From a recent study of Tradescantia stamen hair cells it appears that actin may have a role in defining the plane of cell division. Unlike microtubules, actin is present in the cell cortex and delimits the division site throughout mitosis. Herein, I shall describe actin, its arrangement and putative role in cell plate placement, in another material, living cells of Tradescantia leaf epidermis.The epidermis is peeled from the abaxial surface of young leaves usually without disruption to cytoplasmic streaming or cell division. The peel is stuck to the base of a well slide using 0.1% polyethylenimine and bathed in a solution of 1% mannitol +/− 1 mM probenecid.

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