MICROTUBULE BIOGENESIS AND CELL SHAPE IN <i>OCHROMONAS  </i>

Bouck, G. Benjamin; Brown, David L.

doi:10.1083/jcb.56.2.340

Cited by 161 publications

(15 citation statements)

References 41 publications

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“…It is not certain if the structures listed are a sufficient condition for shape maintenance; the microtubules are clearly a necessary condition for shape tnaintenance in Ochromonas (Brown and Bouck, 1973). A minimal estimate of energy investment for shape maintenance can accordingly be derived from the demonstration by Bouck and Brown (1973) that there are effectively 17 circumferential (around a spherical cell) microtubules in Ochromonas. From the molecular data given by Hepler and Palevitz (1974) and the energy cost of protein synthesis [entry (9) in Table 2] a cell of volume equivalent to that of a spherical cell of 5 fim radius growing at 8x10~* s~^ would have a requirement of 5-3 X 10"" W per cell to produce the 'shape-detertnining' microtubules, i.e.…”

Section: The Non-spherical Cellmentioning

confidence: 99%

“…pellicle (Euglenophyceae) or periplast (Cryptophyceae), a series of cellulose thecal plates each within a membrane-bound vesicle (Dinophyceae), or proteinaceous microtubules (Chrysophyceae) on the inside on the plasmalemma (Buetow, 1968;Dodge, 1973;Bouck and Brown, 1973;Brown andBouck, 1973, 1974;Evans, 1974;Roberts, 1974). It is not certain if the structures listed are a sufficient condition for shape maintenance; the microtubules are clearly a necessary condition for shape tnaintenance in Ochromonas (Brown and Bouck, 1973). A minimal estimate of energy investment for shape maintenance can accordingly be derived from the demonstration by Bouck and Brown (1973) that there are effectively 17 circumferential (around a spherical cell) microtubules in Ochromonas.…”

Section: The Non-spherical Cellmentioning

confidence: 99%

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The Energetics of Freshwater Algae; Energy Requirements for Biosynthesis and Volume Regulation

Raven

1982

New Phytologist

110

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SUMMARYFreshwater algae have an intracellular osmolarity in excess of that of the medium. The tendency for water to enter the cells is resisted, in cells with a mechanically functional cell wall, by the ability of the wall to withstand a turgor pressure equivalent to the intracellular osmolarit^^; in cells lacking such a mechanically functional wall the water which enters is expelled by a contractile vacuole (or its functional equivalent). A comparison of the energy costs of cell volume regulation by these two mechanisois has been carried out making energy costings based on the minimum thermodynamic requirement and on plausible mechanisms for the two processes (wall synthesis and contractile vacuoie function). This analysis yielded the following conclusions.(1) Wall synthesis is a 'growth' process, while contractile vacuole operation is a 'maintenance' process; other things being equal, a cell wall is a preferable mechanism of volume regulation in non-growing cells.(2) For a 5 ftm radius cell with a specific growth rate of 8 x 10"" s~' and a 10 /an radius cell with a rate of 4 x 10~* s~^ the energy input rate for contractile vacuole operation is considerably lower than for wall synthesis on the basis of minimum thermodynamic requirement; the plausible mechanism approach makes the two energy costs quite similar. Decreased growth rates favours the wall over the contractile vacuole mechanism.(3) Increased cell size (10 jwm radius rather than 5 /^na) has similar effects on the energy costs of both volume regulation mechanisms, provided a (cell organic weight)""'^' dependence of intrinsic growth rate is incorporated into the computations, (4) Increased intracellular osmolarity (at constant extracellular osmolarity) causes a directly proportional increase in energy input rate for the cell wall mechanism, and a more than proportional increase in energy cost for the contractile vacuole mechanism.(5) A non-spherical shape increases the energy cost (at constant cell volume) for both the cell wall and the contractile vacuole mechanisms.These conclusions may be used in the interpretation of such phenomena as the lower osmolarity of wall-less than walled cells and the tendency for the resting stages of normally wall-less and flagellate cells to have walls. It appears that the majority of freshwater algae have genetic capabilities to produce both walls and contractile vacuoles for cell volume regulation (e.g, the production of walled cysts by organisms which are normally flagellate, and the production of wall-less motile spores and gametes by normially walled organisms).

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Section: The Non-spherical Cellmentioning

confidence: 99%

Section: The Non-spherical Cellmentioning

confidence: 99%

The Energetics of Freshwater Algae; Energy Requirements for Biosynthesis and Volume Regulation

Raven

1982

New Phytologist

110

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“…An attempt to quantify the extent of paraxial association between microtubules at different levels in the same cell and between different myogenic cells has been made by counting numbers of microtubules lying within about 40 nm (surface-tosurface) of one another in transverse sections. The ratios of paraxially associated microtubules to total numbers of microtubules in consecutive transverse sections have been plotted as a function of cell length for five cells (4,5,6,7,8) (Fig. 9).…”

Section: Organization Of Microtubules In Myogenic Cells At Progressivmentioning

confidence: 99%

“…play in supporting cell shape, particularly with regard to cell elongation (4,7,12,8), and the formation and maintenance of long processes from the cell surface (36,41), and it has been shown with the use of antimicrotubule agents that disruption of microtubules in anisometric cells results in reversible cell shortening or withdrawal of cell processes (5,20,37,38,40). In the systems studied, the common feature of microtubule organization is an orientation of microtubules in the axis of the cellular anisometry, although there may be varying degrees of more complex interactions among the aligned microtubules.…”

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confidence: 99%

Microtubular Organization in Elongating Myogenic Cells

Warren

1974

The Journal of Cell Biology

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Microtubule organization has been studied in serially sectioned myogenic cells in the tail muscle regeneration blastema of Rana pipiens tadpoles. In mesenchymal cells and in some premyoblasts, microtubules radiate from centriolar satellites in a cell center, while in more mature myoblasts a n d myotubes the centrioles no longer appear to serve as organizing centers for microtubules. In all elongate, fusiform myogenic cells, the microtubules are predominately oriented in the longitudinal axis of the cell. Counts of microtubules in transverse sections spaced at regular intervals along the cells show that the absolute number of microtubules is greatest in the thickened midregions of the cells and decreases relatively smoothly toward the tapered ends of the cells. Close paraxial association of microtubules (within 40 nm surface-to-surface) occurs along the entire lengths of cells but appears with greatest frequency in their tapered ends. In two myoblasts, serial sections were used to trace all microtubules in 8-~m long segments of the cells located about midway between the nucleus and one end of the cell. Since tracings show that as many as 50% of the microtubules terminate within the 8-/zm long segment, it seems unlikely that any microtubules extend the entire length of the cell. It is proposed that lateral interactions between paraxial microtubules stabilize the overall microtubular apparatus and contribute to maintenance of the bipolar form of the cells. A three-dimensional model of the complete microtubular array in one of the 8-urn long segments of a myoblast has been constructed. The model reveals that a few microtubules within the segment are bent into smooth curves and loops that could be generated by sliding interaction between paraxial microtubules.Microtubules are recognized as cytoskeletal elements that play an important role in the maintenance of cell shape and in the organization of cellular cytoplasm (29). The organizational patterns of microtubules in cells vary with the shape of the cell and with its function. A common microtubular pattern in cells is a radial dispersion of microtubules from the cell center, a region near the nucleus which usually contains a centriolar pair. Such radially arranged microtubules may be associated with movements of cytoplasmic particles towards or away from the cell center (2,10,22,28,44) or with secretion (21, 45). A good deal of study has been focused on the roles that microtubules 550

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“…The cell shape characteristic of an algal species may be determined by the presence of a cell wall (16,18), cytoskeletal components (4,10,20,27,28), a pellicle beneath the plasma membrane (18,20), or osmotic properties of the cell (22).…”

mentioning

confidence: 99%

Regulation of Cell Shape in Euglena gracilis

Lonergan

1983

Plant Physiol.

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MICROTUBULE BIOGENESIS AND CELL SHAPE IN OCHROMONAS

Cited by 161 publications

References 41 publications

The Energetics of Freshwater Algae; Energy Requirements for Biosynthesis and Volume Regulation

The Energetics of Freshwater Algae; Energy Requirements for Biosynthesis and Volume Regulation

Microtubular Organization in Elongating Myogenic Cells

Regulation of Cell Shape in Euglena gracilis

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