Formation and propagation of cell division-centers in the epidermal layer of internodal segments of Torenia fournieri grown in vitro. Simultaneous surface observations of all the epidermal cells

1974 ◽  
Vol 52 (4) ◽  
pp. 867-872 ◽  
Author(s):  
Hassane Chlyah
Keyword(s):  
Cell Division ◽  
Cytological Study ◽  
Epidermal Layer ◽  
Torenia Fournieri ◽  
Divided Cell ◽  
Probable Origin ◽  
Original Cell ◽  
Surface Observations ◽  
Internodal Segment

A cytological study of bud neoformation was done using a technique of direct observation of whole epidermal strips excised and stained at different stages of development from one side of an internodal segment of Torenia fournieri grown in vitro. It was shown that cell divisions start at random points over the epidermis and spread out progressively and apparently by contagion, forming cell division-centers. These centers are each formed of a central, highly divided cell surrounded by several less divided cells. The number of divisions per original cell decreases with the distance from the highly divided central cell.The probable origin of bud meristems was shown to be either one part of an original cell, one cell, several parts of adjacent cells, or several entire adjacent cells.A competition phenomenon was shown to exist between cell division-centers; few centers form meristematic primordia and only a few of these last form buds (about 20). Thus, on an epidermal strip 10 × 2.5 mm containing about 5000–6000 cells, fewer than 100 cells are implicated in the formation of buds observed morphologically.

scholarly journals SpyAD, a Moonlighting Protein of Group A Streptococcus Contributing to Bacterial Division and Host Cell Adhesion

2014 ◽  
Vol 82 (7) ◽  
pp. 2890-2901 ◽  
Author(s):  
Marilena Gallotta ◽  
Giovanni Gancitano ◽  
Giampiero Pietrocola ◽  
Marirosa Mora ◽  
Alfredo Pezzicoli ◽  
...  
Keyword(s):  
Cell Division ◽  
Mammalian Cells ◽  
Group A Streptococcus ◽  
Host Cells ◽  
Knockout Mutant ◽  
Content Type ◽  
Moonlighting Protein ◽  
Group A

ABSTRACTGroup A streptococcus (GAS) is a human pathogen causing a wide repertoire of mild and severe diseases for which no vaccine is yet available. We recently reported the identification of three protein antigens that in combination conferred wide protection against GAS infection in mice. Here we focused our attention on the characterization of one of these three antigens, Spy0269, a highly conserved, surface-exposed, and immunogenic protein of unknown function. Deletion of thespy0269gene in a GAS M1 isolate resulted in very long bacterial chains, which is indicative of an impaired capacity of the knockout mutant to properly divide. Confocal microscopy and immunoprecipitation experiments demonstrated that the protein was mainly localized at the cell septum and could interactin vitrowith the cell division protein FtsZ, leading us to hypothesize that Spy0269 is a member of the GAS divisome machinery. Predicted structural domains and sequence homologies with known streptococcal adhesins suggested that this antigen could also play a role in mediating GAS interaction with host cells. This hypothesis was confirmed by showing that recombinant Spy0269 could bind to mammalian epithelial cellsin vitroand thatLactococcus lactisexpressing Spy0269 on its cell surface could adhere to mammalian cellsin vitroand to mice nasal mucosain vivo. On the basis of these data, we believe that Spy0269 is involved both in bacterial cell division and in adhesion to host cells and we propose to rename this multifunctional moonlighting protein as SpyAD (StreptococcuspyogenesAdhesion andDivision protein).

scholarly journals Cytokinesis and Midzone Microtubule Organization inCaenorhabditis elegans Require the Kinesin-like Protein ZEN-4

1998 ◽  
Vol 9 (8) ◽  
pp. 2037-2049 ◽  
Author(s):  
William B. Raich ◽  
Adrienne N. Moran ◽  
Joel H. Rothman ◽  
Jeff Hardin
Keyword(s):  
Cell Division ◽  
Null Allele ◽  
Time Lapse ◽  
Equatorial Region ◽  
Microtubule Organization ◽  
Dividing Cells ◽  
Spindle Midzone ◽  
Cross Links ◽  
Complete Cell

Members of the MKLP1 subfamily of kinesin motor proteins localize to the equatorial region of the spindle midzone and are capable of bundling antiparallel microtubules in vitro. Despite these intriguing characteristics, it is unclear what role these kinesins play in dividing cells, particularly within the context of a developing embryo. Here, we report the identification of a null allele ofzen-4, an MKLP1 homologue in the nematodeCaenorhabditis elegans, and demonstrate that ZEN-4 is essential for cytokinesis. Embryos deprived of ZEN-4 form multinucleate single-celled embryos as they continue to cycle through mitosis but fail to complete cell division. Initiation of the cytokinetic furrow occurs at the normal time and place, but furrow propagation halts prematurely. Time-lapse recordings and microtubule staining reveal that the cytokinesis defect is preceded by the dissociation of the midzone microtubules. We show that ZEN-4 protein localizes to the spindle midzone during anaphase and persists at the midbody region throughout cytokinesis. We propose that ZEN-4 directly cross-links the midzone microtubules and suggest that these microtubules are required for the completion of cytokinesis.

The Mechanism of Cell Division in the Cleavage of the Newt's Egg

1955 ◽  
Vol 32 (4) ◽  
pp. 700-733
Author(s):  
G. G. SELMAN ◽  
C. H. WADDINGTON
Keyword(s):  
Cell Division ◽  
Agricultural Research ◽  
Flexural Rigidity ◽  
Elastic Shell ◽  
Spherical Shape ◽  
Vital Staining ◽  
Common Basis ◽  
Agricultural Research Council ◽  
Gel Layer ◽  
Original Cell

The early cleavages in eggs of Triturus alpestris have been studied. Ciné-film technique was used to record changes in the shape of the egg and movements of the surface pigment from which measurements of linear and areal changes were made. Local vital staining was also employed. There was no significant net change in the area of pigmented cortex during cleavage. Before cleavage the egg resembles a viscous liquid drop whose shape is maintained by a uniform elastic shell of Young's Modulus 1.5 x 105 dynes/cm.2 and thickness about 2µ. The egg assumes a more nearly spherical shape immediately before cleavage when the flexural rigidity of the surface layers increases. The flexural rigidity of the cortical layers was found to be maximal at the beginning of cleavage and minimal midway between cleavages. This variation is similar to that previously recorded for cleavage in sea-urchin eggs by Mitchison & Swann (1955), using a similar method. At any particular stage with respect to the cleavage cycle no variation was found in the rigidity at different points on the egg surface. Serial sections show cytoplasmic modification below and ahead of the forming furrow. It was concluded that the new unpigmented cortex, by which the daughter blastomeres remain in contact after cleavage, is first formed as a sheet of gel (which in later stages can be seen to be a double layer) which grows downwards by a process involving gelation at its lower edge, through the cytoplasm from the animal toward the vegetal surface. The gel layer is assumed to contract immediately after its formation, and in this way to produce "dipping in" of the new furrow and all the observed surface movements. These ideas have been developed to form a detailed theory of cleavage in the newt, and suggest a common basis for the consideration of cell division in echinoderm eggs, plants and other forms, on the basis that the necessary increase in surface area is achieved by the formation of new cortex rather than by the expansion of the original cell membrane. The authors wish to thank Prof. M. M. Swann and Dr J. M. Mitchison, both of the Zoology department, Edinburgh University, for helpful discussion during the course of this work. The ciné films used in the course of this study were made by Mr E. Lucey of this department. Measurements of the rate of furrowing and much of the work using a local vital staining method was performed by Miss H. Yates of this department. Dr E. Deuchar, now at University College, London, prepared some of the earlier sectioned material, and we thank Dr M. Fischberg, Oxford University, for a suggestion concerning spindle fibres. The work received the financial support of the Agricultural Research Council.

Modification of cell division by phorbol ester in preimplantation mouse embryos

Development ◽  
1987 ◽  
Vol 101 (2) ◽  
pp. 403-408
Author(s):  
E.T. Mystkowska ◽  
W. Sawicki
Keyword(s):  
Cell Division ◽  
Video Recording ◽  
Mouse Embryos ◽  
Time Intervals ◽  
Cell Divisions ◽  
Stage Of Development ◽  
Preimplantation Mouse Embryos ◽  
Preimplantation Mouse ◽  
Single Blastomeres

2-cell mouse embryos were treated in vitro with a 2 h pulse of phorbol myristate acetate (PMA) at 32nd, 38th and 50th h after hCG, then chased in culture for up to 46 h. Embryos were fixed at various time intervals of chasing, then stained and inspected. Some embryos were carefully inspected with a video recording system, every 1.44s and the cell divisions (cytokinesis) as well as formation of large, single blastomeres, each from two smaller ones, were recorded. PMA pulse let to the suppression of cell divisions. The rate of the suppression was time dependent: with a delay of 0–1, 12 and 18 h between the PMA pulse and time of scheduled cell division about 99, 87 and 44% of 2-cell embryos remained at this stage of development, for at least 10 h, respectively, and 90, 58 and 12% of their blastomeres revealed binuclearity. Since we found that PMA-mediated formation of binuclearity was not the effect of cell fusions, it was assumed that the inhibition of cytokinesis preceded by karyokinesis was responsible for binuclearity. PMA effect on cell divisions was reversible. PMA-treated embryos revealed formation of large, single blastomeres, each from two smaller ones. If cell division appeared after PMA pulse, in about 52% of 3- to 6-cell embryos, the large blastomere formation was recorded in the course of the subsequent 38 h. Large blastomere formation was concluded to be the result of either cell fusion or reversion of incompleted cytokinesis brought about by PMA.

scholarly journals Kinesin molecular motor Eg5 functions during polypeptide synthesis

2011 ◽  
Vol 22 (18) ◽  
pp. 3420-3430 ◽  
Author(s):  
Kristen M. Bartoli ◽  
Jelena Jakovljevic ◽  
John L. Woolford ◽  
William S. Saunders
Keyword(s):  
Cell Division ◽  
Molecular Motor ◽  
Spindle Assembly ◽  
Intact Cells ◽  
Nascent Polypeptide ◽  
Polypeptide Synthesis

The kinesin-related molecular motor Eg5 plays roles in cell division, promoting spindle assembly. We show that during interphase Eg5 is associated with ribosomes and is required for optimal nascent polypeptide synthesis. When Eg5 was inhibited, ribosomes no longer bound to microtubules in vitro, ribosome transit rates slowed, and polysomes accumulated in intact cells, suggesting defects in elongation or termination during polypeptide synthesis. These results demonstrate that the molecular motor Eg5 associates with ribosomes and enhances the efficiency of translation.

scholarly journals The mitotic spindle protein CKAP2 potently increases formation and stability of microtubules

eLife ◽  
2022 ◽  
Vol 11 ◽  
Author(s):  
Thomas S McAlear ◽  
Susanne Bechstedt
Keyword(s):  
Cell Division ◽  
Growth Factor ◽  
Mitotic Spindle ◽  
Apparent Rate Constant ◽  
Microtubule Dynamics ◽  
Proliferation Marker ◽  
Microtubule Growth ◽  
Large Rearrangements ◽  
And Function

Cells increase microtubule dynamics to make large rearrangements to their microtubule cytoskeleton during cell division. Changes in microtubule dynamics are essential for the formation and function of the mitotic spindle, and misregulation can lead to aneuploidy and cancer. Using in vitro reconstitution assays we show that the mitotic spindle protein Cytoskeleton-Associated Protein 2 (CKAP2) has a strong effect on nucleation of microtubules by lowering the critical tubulin concentration 100-fold. CKAP2 increases the apparent rate constant ka of microtubule growth by 50-fold and increases microtubule growth rates. In addition, CKAP2 strongly suppresses catastrophes. Our results identify CKAP2 as the most potent microtubule growth factor to date. These finding help explain CKAP2's role as an important spindle protein, proliferation marker, and oncogene.

scholarly journals The Dynamics of Cell Division in Some Local Potato Varieties Cultivated in Vitro on Micropropagation Medium

2012 ◽  
Vol 45 (3) ◽  
pp. 71-78
Author(s):  
Iustina Brînduşa Ciobanu ◽  
Dana Constantinovici ◽  
L. Creţu
Keyword(s):  
Solanum Tuberosum ◽  
Cell Division ◽  
Mitotic Index ◽  
Accumulation Rate ◽  
Solanum Tuberosum L ◽  
In Vitro Cultures ◽  
Local Varieties ◽  
Skoog Medium ◽  
Murashige Skoog

Abstract This study was performed to reveal the changes in cell division, as a result of the prolonged period of subculture on micropropagation medium, of five local varieties of Solanum tuberosum L. maintained on in vitro collection at Suceava Genebank, Romania. For this purpose it was used the Murashige-Skoog medium (MS- 1962) with addition of 40 g/l sucrose, and 6 mg/l daminozide. The effect of prolonged period of subculture up to two and 12 months was expressed as mitotic index and frequency of cells with abnormal division. Mitotic index ranged from 20.1 to 22.1% after 12 days, between 15.5 - 17.7% after two months and between 17.7 - 19.2% after 12 months of subculture. The results obtained showed that the frequency of aberrant cells increased with the preservation time on the in vitro cultures and their accumulation rate depended on the genotype. Were identified interphases with micronuclei, metaphases with retarded chromosomes, ana-telophases with chromosomal bridges, retarded chromosomes and chromosomal fragments, but their percentage was low in all the genotypes.

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