Cellular events during wound periderm formation in Dioscorea bulbifera bulbils

1989 ◽  
Vol 67 (10) ◽  
pp. 3090-3102 ◽  
Author(s):  
Ina Knobloch ◽  
Günter Kahl ◽  
Pierre Landré ◽  
Arlette Nougarède
Keyword(s):  
Cell Walls ◽  
Superficial Layer ◽  
Cell Nuclei ◽  
Meristematic Cells ◽  
Cellular Events ◽  
Fluorescence And Electron Microscopy ◽  
Deep Wound ◽  
Dioscorea Bulbifera ◽  
Cytoplasmic Ribosomes ◽  
Periderm Formation

The cytological events induced by a deep wound applied to Dioscorea bulbifera bulbils were studied using specific cytochemical methods and fluorescence and electron microscopy. Following wounding, a superficial layer with lignified (3rd h) and weakly suberized (6th h) cell walls formed in the original starchy parenchyma in contact with the wounded cells. Before the first mitoses (72nd h), an extensive dedifferentiation occurred in the underlying layers and involved reactivation of cell nuclei, nucleoli, and plastids. A concomitant aggregation of cytoplasmic ribosomes into polysomes occurred. Starch hydrolysis in the amyloplasts was evident before the first periclinal divisions. Periclinal divisions occurred in the reactivated cells from the second to the fourth layers beneath the wound. These newly meristematic cells could be divided into two to four new cells, leading to a periderm without a true phellogen. These covering layers degenerated during the period of lignification and weak suberization of cell walls. The thickness of the wound periderm depended on the age of the wounded bulbil.

Histological aspects of the cryopreservation of potato

2008 ◽  
Vol 56 (3) ◽  
pp. 341-348
Author(s):  
P. Pepó ◽  
A. Kovács
Keyword(s):  
Cell Wall ◽  
Low Temperatures ◽  
Cell Walls ◽  
Cellular Level ◽  
Adaptive Mechanism ◽  
Epidermal Layer ◽  
Freezing And Thawing ◽  
Meristematic Cells ◽  
Suitable Solution ◽  
Vacuolated Cells

Cryopreservation appears to be a suitable solution for the maintenance of potato germplasms. The protocol described in this paper can be applied for the vitrification and preservation of meristems. During histo-cytological studies it is possible to observe modifications at the cellular level and to understand the adaptive mechanism to low temperatures. Control potato meristem tissue contained a number of meristematic cells with a gradient of differentiation. After freezing there were a large number of vacuolated cells, some of which exhibited broken cell walls and plasmolysis. The thickening of the cell wall, giving them a sinuous appearance, was observed after freezing and thawing the meristems, with ruptures of the cuticle and epidermal layer.

The preprophase band: possible involvement in the formation of the cell wall

1976 ◽  
Vol 22 (2) ◽  
pp. 403-411 ◽  
Author(s):  
M.J. Packard ◽  
S.M. Stack
Keyword(s):  
Cell Wall ◽  
Allium Cepa ◽  
Cell Walls ◽  
Preprophase Band ◽  
Adjacent Cell ◽  
Root Tips ◽  
Meristematic Cells ◽  
Narrow Region ◽  
The Matrix

Numerous vesicles were observed among the microtubules of the “preprophase” band in prophase cells from root tips of Allium cepa. The content of these vesicles looks similar to the matrix of adjacent cell walls, and these vesicles often appear to be involved in exocytosis. In addition, the cell walls perpendicular to the plane of (beneath) the preprophase band are often differentially thickened compared to the walls lying parallel to the plane of the band. Our interpretation of these observations is that the preprophase band may direct or channel vesicles containing precursors of the cell wall to localized regions of wall synthesis. The incorporation of constituents of the cell wall into a narrow region defined by the position of the preprophase band may be a mechanism that ensures unidirecitonal growth of meristematic cells.

scholarly journals Influence of extract from shoots of Taxus baccata var. elegantissima on ultrastructure and tubulin cytoskeleton of meristematic cells of Allium cepa L. roots

2014 ◽  
Vol 71 (3) ◽  
pp. 211-221 ◽  
Author(s):  
Agnieszka Majewska ◽  
Mirosława Furmanowa ◽  
Kazimierz Głowniak ◽  
Joanna Guzewska ◽  
Alicja Zobel ◽  
...  
Keyword(s):  
Allium Cepa ◽  
Chromatin Condensation ◽  
Preprophase Band ◽  
Taxus Baccata ◽  
Cell Nuclei ◽  
Root Tips ◽  
Meristematic Cells ◽  
Allium Cepa L ◽  
Interphase Cells ◽  
Average Size

We investigated the influence of extract from <em>Taxus baccata</em> var. Elegantissima (TbE) shoots in 1:8 dilution, containing paclitaxel in concentration of 81,6 µg/g fresh mass on ultrastructure and tubulin cytoskeleton of meristematic cells of <em>Allium cepa</em> L. root tips. Incubation time 3, 6, 12 and 24 h was followed with postincubation in water for 12 and 24 h. During shorter incubation (till 12 h) the surface of the cell nuclei decreased and chromatin became condensed (in comparison to control) but after 24 h the average surface increased and chromatin condensation decreased. In the course of incubation the average size of plastids and vacuoles increased. Moreover, after treatment mitochondria and plastids showed degradation of ultrastructure, which was reversed after 12 h of postincubation. Immunocytochemical assays demonstrated that in the course of incubation in the ThE extract, the tubulin cytoskeleton became partially disorganised. In most interphase cells, cortical microtubules (MTs) lost their oval transverse orientation. The preprophase band (PPB) position in the cell was often asymmetrical. The MTs array of the karyokinetic spindle and phragmoplast was also disturbed. These alterations were completely reversed during postincubation.

On the nervous system of Saccoglossus cambrensis (Enteropneusta)

1952 ◽  
Vol 236 (634) ◽  
pp. 315-354 ◽  
Keyword(s):  
Fine Particles ◽  
Basal Layer ◽  
Superficial Layer ◽  
Nerve Ring ◽  
Cell Nuclei ◽  
Nerve Fibres ◽  
Giant Axons ◽  
Almost Everywhere ◽  
Peristaltic Contractions ◽  
Nerve Cords

A layer of nerve fibres is present almost everywhere at the base of the epidermis. It consists of a very thin basal layer of irregularly arranged fibres, and generally a thicker, more superficial layer of orientated fibres, which forms the main nerve cords and subsidiary systems of smaller through-conducting bundles. In the proboscis there are numerous longitudinal bundles, an anterior nerve ring round the basal periphery and a nerve loop under the pre-oral ciliary organ. The neurocord appears to be a simple conducting tract. In the collar epidermis numerous bundles are formed posteriorly, connecting with the prebranchial nerve ring. In the trunk the size of the longitudinal cords and the distribution of the general plexus is related to the degree of development of the muscles and cilia. The gut is well equipped with nerve fibres anteriorly, where it is particularly muscular. Practically all the nerve-cell nuclei lie outside the plexus of nerve fibres. They are very numerous and widely distributed. A concentration of bipolar neurones (Hess’s cells) occurs at the proboscis tip. Cells regarded as sensory on histological grounds are abundant round the base of the proboscis and in the groove of the ciliary organ. Large unipolar neurones are concentrated in the neurocord, some possessing ‘giant’ axons, which run posteriorly or anteriorly. The cilia of the epidermis are the chief agents of locomotion, those of the trunk being capable of synchronized reversal. They are aided by peristaltic contractions of the longitudinal muscles, which are controlled by the main longitudinal nerve cords. Burrowing peristalsis is controlled by the dorsal nerve cord of the proboscis. Some reactions to light, to the presence of fine particles and to adrenaline are described. The proboscis is necessary for spontaneous and varied activity, but the considerable degree of co-ordination shown is not due to any localized centre but to a longitudinal reflex path involving the main nerve cords. Rapid contractions of the anterior end are probably due to the giant axons. The peculiarities of the neurocord are difficult to interpret, except as a result of degeneration and paedomorphosis. The greater part of the richly nervous epidermis may be compared with the vertebrate neural plate.

scholarly journals Correlated fluorescence and 3D electron microscopy with high sensitivity and spatial precision

2011 ◽  
Vol 192 (1) ◽  
pp. 111-119 ◽  
Author(s):  
Wanda Kukulski ◽  
Martin Schorb ◽  
Sonja Welsch ◽  
Andrea Picco ◽  
Marko Kaksonen ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Fluorescent Protein ◽  
High Sensitivity ◽  
Cellular Processes ◽  
Cellular Events ◽  
Time Period ◽  
Fluorescence And Electron Microscopy ◽  
3D Electron Microscopy ◽  
3D Electron

Correlative electron and fluorescence microscopy has the potential to elucidate the ultrastructural details of dynamic and rare cellular events, but has been limited by low precision and sensitivity. Here we present a method for direct mapping of signals originating from ∼20 fluorescent protein molecules to 3D electron tomograms with a precision of less than 100 nm. We demonstrate that this method can be used to identify individual HIV particles bound to mammalian cell surfaces. We also apply the method to image microtubule end structures bound to mal3p in fission yeast, and demonstrate that growing microtubule plus-ends are flared in vivo. We localize Rvs167 to endocytic sites in budding yeast, and show that scission takes place halfway through a 10-s time period during which amphiphysins are bound to the vesicle neck. This new technique opens the door for direct correlation of fluorescence and electron microscopy to visualize cellular processes at the ultrastructural scale.

scholarly journals Incorporation of thymidine into onion root meristematic cell nuclei in presence of hydroxyurea and its role in recovery of mitotic activity

2015 ◽  
Vol 46 (4) ◽  
pp. 701-711
Author(s):  
H. Habdas
Keyword(s):  
S Phase ◽  
The Other ◽  
Cell Nuclei ◽  
Onion Root ◽  
Meristematic Cells ◽  
Hydroxyurea Treatment ◽  
Mitotic Block ◽  
Root Meristematic Cells ◽  
Mitotic Figures ◽  
Root Meristematic Cell

Hydroxyurea treatment of onion roots induced mitotic block which was released by transfer of bulbs to water, and also to some extent by addition of cold or <sup>3</sup>H-thymidine to hydroxyurea solutions. In presence of hydroxyurea there was noted very intense incorporation of <sup>3</sup>H-thymidine into cell nuclei, giving labelling index of 40-70%. However, all the mitotic figures appearing in presence of hydroxyurea and <sup>3</sup>H-thymidine were unlabelled. On the other hand, labelled mitotic figures were obtained when roots incubated with <sup>3</sup>H-thymidine in presence of hydroxyurea had been transferred to water. Incorporation of <sup>3</sup>H-uridine was unaffected by hydroxyurea. The results show that hydroxyurea arrests onion root meristematic cells, either in the S phase and the G<sub>2</sub> phase. Enhanced incorporation of <sup>3</sup>H-thymidine in the presence of hydroxyurea, and release by added thymidine of the mitotic block indicate that hydroxyurea induces in onion root meristematic cells a particular shortage of thymidylate.

scholarly journals Studies on the Ontogeny of the Pigment Strand in the Caryopsis of Wheat

1970 ◽  
Vol 23 (5) ◽  
pp. 1153 ◽  
Author(s):  
S-Y Zee ◽  
TP O'brien
Keyword(s):  
Cell Walls ◽  
Meristematic Cells ◽  
Thin Walls ◽  
Pigment Strand ◽  
Days After Anthesis

The grain of wheat has a groove that extends inward nearly to the centre of the grain. At the base of this crease and extending through its length there is a strand of coloured tissue, the pigment strand. At about 3 days after anthesis the cells of this strand of tissue are similar to meristematic cells, possessing thin walls and the usual complement of organelles. At about 9 days after anthesis the cell walls thicken and lignify.

DEVELOPMENTAL STUDIES OF ELODEA CANADENSIS MICHX.: I. MORPHOLOGICAL DEVELOPMENT AT THE SHOOT APEX

1957 ◽  
Vol 35 (1) ◽  
pp. 13-24 ◽  
Author(s):  
Hugh M. Dale
Keyword(s):  
Shoot Apex ◽  
Cell Walls ◽  
Superficial Layer ◽  
Leaf Primordia ◽  
Morphological Development ◽  
Developmental Studies ◽  
Adaxial Surface ◽  
Intercalary Meristem ◽  
Leaf Whorl ◽  
Leaf Insertion

The shoot apex consists of a few initial cells at the tip of a thimble devoid of leaf initials for at least 100 μ. Leaf primorida are initiated from the superficial layer of cells, whereas branch buds arising among the; very youngest leaf primordia are produced deeper in the apex. Chinks occur where three or more cell walls come together. The tissue of the stem for the first 200 μ has no internodes. Two squamulae intervaginales lie on the adaxial surface of each leaf with which their development is associated. Internodes are initiated by the longitudinal growth and division of cells from the bottom of the leaf insertion disks. Cells of the young node divide longitudinally to increase the diameter of the nodal disk and to split the intercalary meristem into segments. Internodes are thus initiated with lacunae. Cells destined to become wood vacuolate at the seventh leaf whorl. Scalariform thickenings are produced but quickly disintegrate along with the rest of the xylem cells leaving a lacuna in the center of the stem. The bast surrounding the central xylem differentiates only slightly, beginning at the 20th leaf whorl, whereas the leaf traces and vertical cortical strands are apparent in younger tissue.

Fungal fimbriae. I. Structure, origin, and synthesis

1975 ◽  
Vol 21 (4) ◽  
pp. 537-546 ◽  
Author(s):  
N. H. Poon ◽  
A. W. Day
Keyword(s):  
Cell Walls ◽  
High Speed ◽  
De Novo ◽  
Sucrose Solution ◽  
Gram Negative Bacteria ◽  
Fine Hair ◽  
Ustilago Violacea ◽  
Anther Smut ◽  
De Novo Protein Synthesis ◽  
Cytoplasmic Ribosomes

Fine hair-like appendages on the cell walls of the anther smut Ustilago violacea are described. These hairs are termed fimbriae because of their close similarity to the fimbriae (pili) found on certain Gram-negative bacteria. Cells of U. violacea may carry more than 200 fimbriae varying in length from about 0.5 μm to over 10 μm, and having a diameter of about 60–70 Å. Some fimbriae produce knobs similar to those found on bacterial sex fimbriae. Log-phase cells are the most densely fimbriated, while stationary phase cells are devoid of fimbriae. The cells can be de-fimbriated by sonication, high-speed agitation, or centrifugation through a 40% sucrose solution. The fimbriae can regenerate in these defimbriated cells in about 1 h. This regeneration is inhibited by both cycloheximide and rifampin, but not by chloramphenicol and therefore appears to depend on de novo protein synthesis on cytoplasmic ribosomes. Similar long fimbriae are found on U. maydis and Leucosporidium (Candida) scottii. Short fimbriae, about 0.5 μm long, were found on all the other species of yeast-like fungi examined (Rhodotorula, Saccharomyces, Schizosaccharomyces, Hansenula, Lipomyces, Nadsonia, and Torulopsis spp.).

scholarly journals An Entropy-Based Automated Cell Nuclei Segmentation and Quantification: Application in Analysis of Wound Healing Process

2013 ◽  
Vol 2013 ◽  
pp. 1-10 ◽  
Author(s):  
Varun Oswal ◽  
Ashwin Belle ◽  
Robert Diegelmann ◽  
Kayvan Najarian
Keyword(s):  
Wound Healing ◽  
Probability Distributions ◽  
Healing Process ◽  
Input Image ◽  
Wound Healing Process ◽  
Threshold Values ◽  
Cell Nuclei ◽  
Nuclei Segmentation ◽  
Cellular Events ◽  
Histological Images

The segmentation and quantification of cell nuclei are two very significant tasks in the analysis of histological images. Accurate results of cell nuclei segmentation are often adapted to a variety of applications such as the detection of cancerous cell nuclei and the observation of overlapping cellular events occurring during wound healing process in the human body. In this paper, an automated entropy-based thresholding system for segmentation and quantification of cell nuclei from histologically stained images has been presented. The proposed translational computation system aims to integrate clinical insight and computational analysis by identifying and segmenting objects of interest within histological images. Objects of interest and background regions are automatically distinguished by dynamically determining 3 optimal threshold values for the 3 color components of an input image. The threshold values are determined by means of entropy computations that are based on probability distributions of the color intensities of pixels and the spatial similarity of pixel intensities within neighborhoods. The effectiveness of the proposed system was tested over 21 histologically stained images containing approximately 1800 cell nuclei, and the overall performance of the algorithm was found to be promising, with high accuracy and precision values.

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