Computer-aided 3-D reconstruction of interphase epidermal cells of Datura stramonium reveals assembly

Development ◽  
1989 ◽  
Vol 106 (3) ◽  
pp. 531-541
Author(s):  
D.J. Flanders ◽  
D.J. Rawlins ◽  
P.J. Shaw ◽  
C.W. Lloyd

From immunofluorescence microscopy it has been cortical microtubules form whole-cell arrays. This has clearly seen in cylindrical hairs where the existence testifies to the continuity of the array around the cell. It is not, however, clear how microtubules pack polyhedral cells with multiple, angled facets. In problem, elongated and isodiametric cells in the stramonium L. were subjected to anti-tubulin avoiding distortion by cellulase treatment and air- sections were then deblurred by computer, the digitized, reconstructed and then rotated in order to arrangement of microtubules along the anticlinal walls This established several things. Microtubules tend to any one cell face; they form transverse, oblique or except that some walls bear a crisscross arrangement. cells, microtubules clearly form helices. In the cells, transversely wound microtubules are confirmed continuous from one face to another and probably, constitute helices. Microtubules on oblique end walls continue onto the side walls and do not form a microtubules can be ordered upon two adjacent facets, with respect to the stem's axis need not necessarily both facets, i.e. overall alignment can change at the isodiametric epidermal cells, microtubules can one cell facet to another. However, where microtubules anticlinal walls spill over onto a periclinal wall at a crisscross arrangement is set up. This is attributed geometrical problem of fitting parallel lines around polyhedra. Despite crossing over one another, the walls are nevertheless continuous with MTs on the side conclusion, in elongated cells the arrays still various pitch: in isodiametric cells (where the walls non-orthogonal angles to one another) the integrity of appears to be preserved by microtubules crossing over what is termed a ‘sacrificial’ face. The overriding microtubules to form an integral array regardless of

Experiments were made on thin sheets of water projected vertically downwards from a slit between side walls. Three kinds of self-induced disturbance were investigated. (i) If the water fell into a pool and air was confined by a back wall behind the sheet, oscillations were set up of the type sometimes seen at a weir across a river. They could be diminished or stopped by splitters inserted at the slit to form A-shaped breaks in the sheet so that resonance between the sheet and the trapped air was reduced. Complete suppression was difficult to achieve unless the obstruction was made unacceptably large; it is better to allow the stream to fall unimpeded on to some kind of bridge structure placed above the pool and permitting free access of air to the space behind. A few readings were taken with the sheet projected horizontally, thus simulating flow over a weir more closely. (ii) With the back wall removed and a sufficient height of fall, the sheet developed irregular oscillations and abruptly disintegrated. This effect was largely caused by reaction with the surrounding air, for it did not occur when the experiment was repeated in a vacuum chamber. (iii) If the velocity of projection from the slit was diminished below that of antisymmetri-cal waves, a continuous sheet was impossible and the water emerged in streams. The V-shaped sheet was examined that was formed when the discharge was reduced sufficiently for contact with the side walls to be lost. The wavelength of the stationary train of ripples that appeared above the edges of the sheet was found to be given by the usual theory which assumes gravity to be negligible compared with surface tension.


1990 ◽  
Vol 110 (4) ◽  
pp. 1111-1122 ◽  
Author(s):  
D J Flanders ◽  
D J Rawlins ◽  
P J Shaw ◽  
C W Lloyd

To investigate the spatial relationship between the nucleus and the cortical division site, epidermal cells were selected in which the separation between these two areas is large. Avoiding enzyme treatment and air drying, Datura stramonium cells were labeled with antitubulin antibodies and the three-dimensional aspect of the cytoskeletons was reconstructed using computer-aided optical sectioning. In vacuolated cells preparing for division, the nucleus migrates into the center of the cell, suspended by transvacuolar strands. These strands are now shown to contain continuous bundles of microtubules which bridge the nucleus to the cortex. These nucleus-radiating microtubules adopt different configurations in cells of different shape. In elongated cells with more or less parallel side walls, oblique strands radiating from the nucleus to the long side walls are presumably unstable, for they are progressively realigned into a transverse disc (the phragmosome) as broad, cortical, preprophase bands (PPBs) become tighter. The phragmosome and the PPB are both known predictors of the division plane and our observations indicate that they align simultaneously in elongated epidermal cells. These observations suggest another hypothesis: that the PPB may contain microtubules polymerized from the nuclear surface. In elongated cells, the majority of the radiating microtubules, therefore, come to anchor the nucleus in the transverse plane, consistent with the observed tendency of such cells to divide perpendicular to the long axis. In nonrectangular isodiametric epidermal cells, which approximate regular hexagons in section, the radial microtubular strands emanating from the nucleus tend to remain associated with the middle of each subtending cell wall. The strands are not reorganized into a single dominant transverse bar, but remain as a starlike array until mitosis. PPBs in these cells are not as tight; they may only be a sparse accumulation of microtubules, even forming along non-diametrical radii. This arrangement is consistent with the irregular division patterns observed in epidermal mosaics of isodiametric D. stramonium cells. The various conformations of the radial strands can be modeled by springs held in two-dimensional hexagonal frames, and by soap bubbles in three-dimensional hexagonal frames, suggesting that the division plane may, by analogy, be selected by minimal path criteria. Such behavior offers a cytoplasmic explanation of long-standing empirically derived "rules" which state that the new cell wall tends to meet the maternal wall at right angles. The radial premitotic strands and their analogues avoid taking the longer path to the vertex of an angle where a cross wall is already present between neighboring cells.(ABSTRACT TRUNCATED AT 400 WORDS)


1993 ◽  
Vol 41 (9) ◽  
pp. 1373-1381 ◽  
Author(s):  
S Nishikawa ◽  
F Sasaki

We examined proteoglycans (PGs) in amphibian epidermal cells by immunofluorescence microscopy. Immunoelectron microscopy with pre- and post-embedding methods, combined with HRP- or gold-conjugated secondary antibody, revealed ultrastructural localization of glycosaminoglycans (GAGs). Embryonic epidermis secretion granules in Xenopus laevis contained chondroitin 6-sulfate and unsulfated chondroitin. Immature secretion granules were also labeled with anti-chondroitin 6-sulfate and anti-chondroitin. A step-wise digestion experiment on chondroitinase ABC revealed that fine filaments in the secretion granules were chondroitin sulfate chains. Inhibition experiments with brefeldin A revealed that the life of a secretion granule was 5-10 hr, suggesting that GAG secretion from embryonic epidermis is routed through a regulated pathway.


2007 ◽  
Vol 553 ◽  
pp. 130-135
Author(s):  
Gabriel Plascencia ◽  
Torstein A. Utigard ◽  
Juliana Gutiérrez ◽  
David Jaramillo ◽  
Vicente Mayagoitia ◽  
...  

A three dimensional numerical heat transfer model has been developed to estimate the heat flux trough furnace side walls protected with water cooled cooling fingers. The model was set up by means of the finite element method. Materials with different thermal conductivity were modelled and the results obtained with the mathematical model were compared with experimental data. In every case, it was found excellent agreement between the experimental data and the model computations.


Development ◽  
1973 ◽  
Vol 29 (3) ◽  
pp. 539-547
Author(s):  
H. R. Kobel ◽  
R. B. Brun ◽  
M. Fischberg

The developmental potencies of melanophores, ciliated epidermal cells and cells from an established line were tested by means of nuclear transplantation into enucleated Xenopus eggs. Donor nuclei from ciliated epidermal cells of hatching tadpoles never gave rise, after transplantation, to development beyond the blastula stage; nuclei from non-ciliated cells of the same larvae, on the other hand, could fully replace a zygote nucleus. Melanophore nuclei taken from the tailfin of advanced larvae (stage 56) gave rise to blastulae and, in one case, an incipient invagination was observed. Melanophore nuclei taken from tissue cultures, set up from hatching tadpoles, proved to be competent for leading development as far as the heartbeat stage, (stage 33/34), the embryo showing well-elaborated eye Anlagen, muscles, notochord, cement gland, etc. Nuclei from the highly aneuploid established cell-line A-8 were able to give rise to hatching-stage embryos. These results suggest that some condition, provided by culturing, influences the differentiated state so as to improve the chances of the donor nucleus co-operating with the egg's developmental programme. The important change might be the state of proliferation attained in cultured cells.


2019 ◽  
Vol 572 (5) ◽  
pp. 11-15
Author(s):  
Janusz Kompała ◽  
Rafał Wiśniowski

The article presents a method of limiting exposure to noise in the vicinity or workstations of conveyor drive services. This is done by setting up the conveyor belt personnel’s workstations within special technological recesses. The core of the presented solution consists in the design of an optimal set up of the technological recess, which in turn has enabled the realisation of production activities with OSH taken into account. The necessary requirement was a simultaneous achievement of the value of the equivalent noise level A LAeq below the value of relevant health standards. The results of the measurement were superimposed on the schematics of the mining excavation, and thus decided about the placement of the solution. New workstations were created and located according to the same schematics with the use of one-way exit with roof and the front wall and the side walls made of straight cross-bars of V29 profiles. Additionally, to improve the acoustic climate, the constructed technological recesses went through the acoustic adaptation performed with the use of sound absorbing material. The solution has been implemented in Węglokoks Kraj Sp. z o.o. KWK „Bobrek - Piekary”.


2013 ◽  
Vol 765-767 ◽  
pp. 785-788 ◽  
Author(s):  
Hui Li ◽  
Yu Ji Li ◽  
Jing Xiao Zhang ◽  
Cai Wu Lu

The University Timetable Problems in Civil Engineering hinders the multi-targeting combinatorial optimization of teaching resources in colleges and universities. In this paper, it is studied how to adopt ant colony genetic algorithm to set up the course schedule system for civil engineering in colleges and universities, which makes the population form partitions according to rules in the genetic process, spray pheromones in the partitions, with the chromosome fitness and the population partitions crossing over with each other, to form a positive feedback system. As the experiment shows, through this method, the searching space can be reduced effectively, and the complexity of programs is simplified, so the time spent in generating optimal course schedules can be shortened.


1989 ◽  
Vol 67 (12) ◽  
pp. 3506-3512 ◽  
Author(s):  
Taizo Hogetsu

The first leaf of Avena sativa L., a monocotyledonous plant, grows in a region that lies within 10 mm of the base of the leaf. Cells in that region elongate longitudinally but hardly expand laterally. The orientation of cortical microtubules in the elongating region is transverse in both epidermal and parenchymal cells. The same features of the arrangement of microtubules are also observed in the leaves of Zea mays. Cellulose microfibrils in the cell wall are coaligned with microtubules, lying approximately transverse to the axis of elongation, as if they function as hoops to facilitate the longitudinal elongation of the cell. The cells of growing leaves of Pisum sativum L., a dicotyledonous plant, expand superficially in every direction at every point on the leaf. Cortical microtubules lining the outer walls of epidermal cells are arranged randomly or in parallel. The parallel microtubules are oriented in various directions. In the outer walls of epidermal cells of growing leaves, areas with different predominant orientations of microfibrils are found within a single cell, consistent with the arrangement of microtubules. These results indicate that the orientation of cortical microtubules is correlated with the orientation of microfibrils and the direction of growth in growing leaves of both monocotyledons and dicotyledons, suggesting the involvement of cortical microtubules in control of the direction of growth in leaves.


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