scholarly journals Influence of hydroxyurea on cell divisions and microtubular cytoskeleton in Allium cepa root meristem

2014 ◽  
Vol 65 (1-2) ◽  
pp. 179-185 ◽  
Author(s):  
H. Q. Zhang ◽  
Y. Q. Li ◽  
M. Kuraś ◽  
J. Bednara ◽  
M. Cresti
Keyword(s):  
Mitotic Activity ◽  
Apical Meristem ◽  
Root Meristem ◽  
Distal Region ◽  
Mitotic Spindles ◽  
Immunofluorescence Method ◽  
Cell Divisions ◽  
Microtubular Cytoskeleton ◽  
Tubulin Immunofluorescence ◽  
Short Time

In onion roots, hydroxyurea (HU) causes a gradual depression of mitotic activity which ceases after 24-36 hrs. The effect is reversible; divisions begin after several hours of recovery and after 12-14 hrs about 90% cells undergo mitosis. Mitotic activity commences in the distal region of the apical meristem, and as a wave it spreads towards the apex. In the roots treated with HU for a short time, the tubulin immunofluorescence method reveals normal arrays of microtubules (MTs). After 36 hrs of HU treatment there are only cortical and endocytoplasmatic MTs. In the recovering roots, preprophase bands (PB) mitotic spindles and phragmoplasts appear. Some PBs are split into two parallel rings. These abnormal PBs mostly occur in elongated cells. Apart from this, HU does not appear to have any significant influence on microtubular organization.

The indirect effect of exogenous auxin on initiation of cell divisions in wheat root expiants (Triticum aestivum) during callus induction

1989 ◽  
Vol 67 (7) ◽  
pp. 1979-1984
Author(s):  
Dalia T. Kudirka ◽  
Blanche B. Brightwell
Keyword(s):  
Triticum Aestivum ◽  
Mitotic Activity ◽  
Apical Meristem ◽  
Primary Root ◽  
Root Apex ◽  
Wheat Root ◽  
Root Apical Meristem ◽  
Root Explants ◽  
Cell Divisions ◽  
Synthetic Auxins

Mitotic activity (indices) was measured in apical and nonapical regions of primary root explants excised from 2-day-old germinating seedlings of wheat (Triticum aestivum Thell em L.) and cultured in the presence of the synthetic auxins 3,6-dichloro-O-anisic acid (dicamba) and 2,4-dichlorophenoxyacetic acid (2,4-D). Mitotic activity in the root apical meristem decreased with increasing concentration of auxin in the culture media. Correlated with the decrease of mitotic activity in the root apical meristem was an increase of mitotic activity in nonapical regions of the root. The degree of cell division activity initiated in nonapical regions of the root was (i) inversely proportional to the degree of inhibition of cell divisions in the root apex, but (ii) independent of the concentration of auxin in the culture medium. These data suggest that the primary effect of these synthetic auxins on mitotic activity in wheat root explants is to suppress cell divisions in the primary root apex and not to stimulate cell divisions in the nonapical regions of the root. Cell cycle control in nonapical regions of the root appears to be a function of factor(s) emanating from mitotically active cells of the primary apical meristem.

An Alternative Test Using Algal Cultures for Testing Chemicals for Toxicity

1993 ◽  
Vol 21 (2) ◽  
pp. 196-201
Author(s):  
Søren Achim Nielsen ◽  
Thomas Hougaard
Keyword(s):  
Size Distribution ◽  
Mitotic Activity ◽  
Time Scale ◽  
Test System ◽  
Short Time Scale ◽  
Toxic Substances ◽  
Alternative Test ◽  
Short Time ◽  
Algal Cultures ◽  
Test Cultures

An alternative test is presented, in which algal cultures are used for testing toxic substances. This test system is based on variations in the size distribution of cells in test cultures as a measurement of growth. Thus, inhibition of mitotic activity is used as a measurement for toxic effects. The test can be performed on a short time-scale and is very sensitive to even weak toxic doses.

Unequal cleavage in leech embryos: zygotic transcription is required for correct spindle orientation in subset of early blastomeres

Development ◽  
1996 ◽  
Vol 122 (2) ◽  
pp. 599-606
Author(s):  
S.T. Bissen ◽  
C.M. Smith
Keyword(s):  
Cell Division ◽  
Early Period ◽  
Spindle Orientation ◽  
Mitotic Spindles ◽  
Maternal Control ◽  
Transcription Analysis ◽  
Cell Divisions ◽  
Zygotic Transcription ◽  
Different Types ◽  
Alpha Amanitin

Leech embryos undergo invariant sequences of equal and unequal cell divisions to give rise to identifiable progeny cells. While many of the early cleavages are under maternal control, the divisions of a subset of early blastomeres (the large cells of the D' lineage) are perturbed after the inhibition of zygotic transcription. Analysis of the different types of cells produced in embryos injected with the transcriptional inhibitor, alpha-amanitin, revealed that the symmetry of cell division is perturbed in these large D'-derived cells during this early period of development. These cells, which would normally undergo a series of equal and unequal cleavages, always undergo equal cleavages after the inhibition of zygotic transcription. It appears that zygotically transcribed gene product(s) are required in the large cells of the D' lineage to orient the mitotic spindles properly for these unequal cell cleavages.

scholarly journals Study of Mitotic Activity and Chromosomal Behaviour in Root Meristem of Allium cepa L. Treated with Magnesium Sulphate

2009 ◽  
Vol 15 ◽  
pp. 83-88 ◽  
Author(s):  
Prabhakar Bhatta ◽  
S. R. Sakya
Keyword(s):  
Key Words ◽  
Mitotic Activity ◽  
Allium Cepa ◽  
Biological System ◽  
Magnesium Sulphate ◽  
Root Meristem ◽  
Chromosomal Abnormalities ◽  
Inhibitory Effect ◽  
Duration Of Treatment ◽  
Chromosomal Behaviour

The mitotic activity and chromosomal behaviour was observed in four different concentrations of magnesium sulphate at four different duration of treatment using Allium cepa as a biological system. Mito-inhibitory effect of the compound was observed in higher concentration. The compound was capable of producing various chromosomal abnormalities indicating the cytostatic and clastogenic properties of magnesium sulphate. Key words: Allium cepa, magnesium sulphate, mitotic index, phase indices.doi: 10.3126/eco.v15i0.1947 ECOPRINT 15: 83-88, 2008

scholarly journals Influence of 1-p-D-arabinofuranosylcytosine on mitotic activity of apical meristem of onion (Allium cepa L.) roots

2015 ◽  
Vol 47 (1–2) ◽  
pp. 173-187 ◽  
Author(s):  
M. Kuraś ◽  
A. Malinowska
Keyword(s):  
Mitotic Activity ◽  
Chromosome Aberration ◽  
Allium Cepa ◽  
Cytosine Arabinoside ◽  
Adventitious Roots ◽  
Apical Meristem ◽  
Allium Cepa L ◽  
Cells With Micronuclei

The influence of increasing cytosine arabinoside (ara-C) concentration (50, 100, 300 and 500 μg/ml) on the mitotic activity of the apical meristem of onion adventitious roots was investigated during 24-h incubation in ara-C and postincubation in water. Incubation in ara-C inhibits reversibly mitosis, the degree of inhibition being dependent on the concentration used. 50 μg/ml ara-C causes only a slight and transitional mitotic depression, while 100—500 μg/ml reduces the per cent of mitoses in various degrees after 12-h incubation whereas after 24 h all concentrations (100—500) reduce mitosis to the same level of about 2 per cent (80% inhibition). During postincubation in water there occurs after treatment with 100—500 μg/ml ara-C, a wave of highly synchronized mitoses with a peak after 12 h. The highest frequency of synchronized mitoses (60°/o) appeared in roots treated with 300 μg/ml ara-C. The main wave is preceded by a small one with a peak after 2-4 h of postincubation. This seems to be the consequence of phases S and G<sub>2</sub> inhibition by ara-C. It was found that under the influence of ara-C the per cent of mitoses with chromosome aberration and of cells with micronuclei increased only slightly.

scholarly journals Class I KNOX Is Related to Determinacy during the Leaf Development of the Fern Mickelia scandens (Dryopteridaceae)

2020 ◽  
Vol 21 (12) ◽  
pp. 4295 ◽  
Author(s):  
Rafael Cruz ◽  
Gladys F. A. Melo-de-Pinna ◽  
Alejandra Vasco ◽  
Jefferson Prado ◽  
Barbara A. Ambrose
Keyword(s):  
Leaf Development ◽  
Apical Meristem ◽  
Class I ◽  
Seed Plants ◽  
Histone H4 ◽  
Knox Genes ◽  
Apical Meristems ◽  
Cell Divisions ◽  
Shoot Apical Meristems

Unlike seed plants, ferns leaves are considered to be structures with delayed determinacy, with a leaf apical meristem similar to the shoot apical meristems. To better understand the meristematic organization during leaf development and determinacy control, we analyzed the cell divisions and expression of Class I KNOX genes in Mickelia scandens, a fern that produces larger leaves with more pinnae in its climbing form than in its terrestrial form. We performed anatomical, in situ hybridization, and qRT-PCR experiments with histone H4 (cell division marker) and Class I KNOX genes. We found that Class I KNOX genes are expressed in shoot apical meristems, leaf apical meristems, and pinnae primordia. During early development, cell divisions occur in the most distal regions of the analyzed structures, including pinnae, and are not restricted to apical cells. Fern leaves and pinnae bear apical meristems that may partially act as indeterminate shoots, supporting the hypothesis of homology between shoots and leaves. Class I KNOX expression is correlated with indeterminacy in the apex and leaf of ferns, suggesting a conserved function for these genes in euphyllophytes with compound leaves.

scholarly journals THE EFFECT OF A MEDIUM DOSE (430 ROENTGENS) OF X-RAY IRRADIATION ON RESTING CELLS OF THE LIVER

1962 ◽  
Vol 13 (2) ◽  
pp. 261-268 ◽  
Author(s):  
Antoni Horst ◽  
Tadeusz Rudnicki
Keyword(s):  
Mitotic Activity ◽  
Time Interval ◽  
Resting Cells ◽  
Experimental Animals ◽  
X Ray ◽  
White Rats ◽  
Mitotic Figures ◽  
Short Time ◽  
Single Medium ◽  
Medium Dose

The mitotic activity of regenerating liver cells after a single dose (430 r) of x-ray irradiation was studied. In every group of the experimental animals (white rats), the mitotic activity (mitotic index) and the number of abnormal mitotic figures were determined. The results indicated that resting cells irradiated a short time before mitotic activity showed reactions similar to those of cells irradiated during mitotic activity. The disturbances in the irradiated mitotically active cells were only quantitatively different from those in the irradiated resting cells. The disturbances in the irradiated resting cells depended upon the time interval between the irradiation and the beginning of mitotic activity stimulated by partial hepatectomy. It was found that the shorter the time interval, the more pronounced were the disturbances and the more similar they became to those of irradiated mitotically active cells. Conversely, the longer the time interval between the irradiation and the beginning of mitotic activity, the less pronounced were the disturbances and the more similar they became to those of the non-irradiated control cells. A discussion is presented as to whether or not the lesions of resting cells caused by a single medium dose of x-ray irradiation are reversible, and whether such lesions are only brought to light by the process of mitosis or whether the process of mitosis renders it possible for these lesions to develop.

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