scholarly journals Regulation of cell shape in Euglena gracilis. IV. Localization of actin, myosin and calmodulin

1985 ◽  
Vol 77 (1) ◽  
pp. 197-208
Author(s):  
T.A. Lonergan
Keyword(s):  
Plasma Membrane ◽  
Euglena Gracilis ◽  
Cell Shape ◽  
Biological Clock ◽  
Free Medium ◽  
Calmodulin Antagonist ◽  
Cell Rounding ◽  
Contractile System ◽  
High Degree ◽  
Shape Changes

The immunofluorescence patterns for actin, myosin, calmodulin and tubulin were observed in Euglena gracilis Klebs strain Z during the biological clock-controlled shape changes observed with division-synchronized cells, and during two shock responses that induce cell rounding. The fluorescence patterns for actin, myosin, calmodulin and tubulin show a high degree of coincidence and are visualized as lines running parallel to, and having the same spacing as, the pellicle strips beneath the plasma membrane. The fluorescence patterns remain intact during the daily shape changes, implying that the shape changes do not result from cycles of polymerization and depolymerization of the microtubules and microfilaments. Resuspension of cells in Ca2+-free medium induces cell rounding of many of the cells. The actin and calmodulin patterns are partially disrupted by the Ca2+-free resuspension, while the myosin pattern is almost totally disrupted. Microtubules are unaffected by this treatment. Prior exposure of cells to the calmodulin antagonist trifluoperazine or to the microfilament-stabilizing peptide phalloidin stabilize the actin, myosin and calmodulin patterns against disruption by the Ca2+-free resuspension and other shock responses. The possibility of an actomyosin contractile system controlled by calmodulin is discussed.

Regulation of cell shape in Euglena gracilis. V. Time-dependent responses to Ca2+ agonists and antagonists

1988 ◽  
Vol 89 (3) ◽  
pp. 365-371
Author(s):  
T.A. Lonergan ◽  
L.C. Williamson
Keyword(s):  
Euglena Gracilis ◽  
Cell Elongation ◽  
Biological Clock ◽  
Bay K 8644 ◽  
Unexpected Result ◽  
Channel Blockers ◽  
Light Cycle ◽  
Free Medium ◽  
Simultaneous Exposure ◽  
Cell Rounding

The daily changes in cellular shape observed in growth-synchronized cultures of Euglena gracilis Klebs strain Z, were altered by exposure to Ca2+ channel agonists and antagonists. The response of the cells to these pharmacological agents depended, in part, on the time in the growth cycle that the cells were exposed. The Ca2+ channel blockers verapamil and nifedipine and the intracellular Ca2+ antagonist TMB-8 all caused cell rounding when elongated cells from the middle of the light cycle were treated. These results were the same as with other methods used to deprive cells of extracellular Ca2+, such as exposure to EGTA or resuspension in Ca2+-free medium. The cell response in mid light cycle to the channel blockers was reversible by simultaneous exposure to CaCl2, and the nifedipine response was also reversed by simultaneous exposure to the structurally related Ca2+ agonist BAY-K 8644. Exposure of cells in the first hour of the light cycle to verapamil, nifedipine or TMB-8 caused an unexpected result. Instead of preventing the round cells from elongating in the first portion of the light cycle, as do LaCl3, EGTA or resuspension in Ca2+-free medium, a greater than expected percentage of elongated cells was found in the treated population. This represents the first instance in which the biological clock control over the rate and extent of cell elongation was accelerated. The calcium agonist CGP-28392 did not have an effect on cell elongation in the early portion of the light cycle but caused cell rounding in the middle of the light cycle. The calcium agonist BAY-K 8644 did not cause any shape changes alone, but was capable of reversing the effects of nifedipine in the middle of the light cycle.

Regulation of cell shape in Euglena gracilis. II. The effects of altered extra- and intracellular Ca2+ concentrations and the effect of calmodulin antagonists

1984 ◽  
Vol 71 (1) ◽  
pp. 37-50
Author(s):  
T.A. Lonergan
Keyword(s):  
Euglena Gracilis ◽  
Cell Shape ◽  
Ionophore A23187 ◽  
Free Medium ◽  
Calmodulin Antagonists ◽  
Daily Cycle ◽  
Cell Shapes ◽  
Euglena Gracilis Z ◽  
Shape Changes ◽  
Synchronized Cultures

When cultures of Euglena gracilis Z., normally grown in medium containing 180 microM-Ca2+, are resuspended in Ca2+-free medium cells assume round shapes within 10 min, from which they recover slowly when Ca2+ is returned to the cultures. Cultures grown in 10 microM-Ca2+ do not display the typical circadian rhythm in cell shape even though the photosynthesis and cell division circadian rhythms are unaffected. Elevating intracellular Ca2+ levels by the addition of the Ca2+ ionophore A23187 prevents cells from undergoing the two daily shape changes characteristic of growth-synchronized cultures, but does not alter the ability to maintain the cell shapes found at the time of ionophore addition. When the calmodulin inhibitors trifluoperazine or chlorpromazine are added to cultures, the cells always respond by rounding. Cells are not able to maintain any cell shape other than spherical in the presence of these inhibitors and therefore cannot change shape throughout the daily cycle as is found in the control populations.

Regulation of cell shape in Euglena gracilis. III. Involvement of stable microtubules

1985 ◽  
Vol 74 (1) ◽  
pp. 219-237
Author(s):  
C.L. Lachney ◽  
T.A. Lonergan
Keyword(s):  
Euglena Gracilis ◽  
Cell Shape ◽  
Microtubule Assembly ◽  
Live Cells ◽  
Microtubule Depolymerization ◽  
Cytoplasmic Microtubule ◽  
Intact Cells ◽  
Calmodulin Antagonist ◽  
Cell Shapes ◽  
In Cells

The role of cytoplasmic microtubules in a recently reported biological clock-controlled rhythm in cell shape of the alga Euglena gracilis (strain Z) was examined using indirect immunofluorescence microscopy. The resulting fluorescent patterns indicated that, unlike many other cell systems, Euglena cells apparently change from round to long to round cell shape without associated cytoplasmic microtubule assembly and disassembly. Instead, the different cell shapes were correlated with microtubule patterns, which suggested that movement of stable microtubules to accomplish cell shape changes. In live intact cells, these microtubules were demonstrated by immunofluorescence to be stable to lowered temperature and elevated intracellular Ca2+ levels, treatments that are commonly used to depolymerize microtubules. In cells extracted in detergent at low temperature or in the presence of elevated Ca2+ levels, the fluorescent image of the microtubules was disrupted. Transmission electron microscopy confirmed the loss of one subset of pellicle microtubules. The difference in microtubule stability to these agents between live intact cells and cells extracted in detergent suggested the presence of a microtubule-stabilizing factor in live cells, which is released from the cell by extraction with detergent, thereby permitting microtubule depolymerization by Ca2+ or lowered temperature. The calmodulin antagonist trifluoperazine prevented the Ca2+-induced disruption of the fluorescent microtubule pattern in cells extracted in detergent. These results implied the involvement of calmodulin in the sensitivity to Ca2+ of the microtubules of cells extracted in detergent.

scholarly journals Crosstalk between basal extracellular matrix adhesion and building of apical architecture during morphogenesis

Biology Open ◽  
2021 ◽  
Vol 10 (11) ◽  
Author(s):  
Mariana Barrera-Velázquez ◽  
Luis Daniel Ríos-Barrera
Keyword(s):  
Extracellular Matrix ◽  
Plasma Membrane ◽  
Cell Shape ◽  
Plasma Membranes ◽  
Tube Formation ◽  
Apical Plasma Membrane ◽  
Complex Structures ◽  
Apicobasal Polarity ◽  
Basal Plasma ◽  
Shape Changes

ABSTRACT Tissues build complex structures like lumens and microvilli to carry out their functions. Most of the mechanisms used to build these structures rely on cells remodelling their apical plasma membranes, which ultimately constitute the specialised compartments. In addition to apical remodelling, these shape changes also depend on the proper attachment of the basal plasma membrane to the extracellular matrix (ECM). The ECM provides cues to establish apicobasal polarity, and it also transduces forces that allow apical remodelling. However, physical crosstalk mechanisms between basal ECM attachment and the apical plasma membrane remain understudied, and the ones described so far are very diverse, which highlights the importance of identifying the general principles. Here, we review apicobasal crosstalk of two well-established models of membrane remodelling taking place during Drosophila melanogaster embryogenesis: amnioserosa cell shape oscillations during dorsal closure and subcellular tube formation in tracheal cells. We discuss how anchoring to the basal ECM affects apical architecture and the mechanisms that mediate these interactions. We analyse this knowledge under the scope of other morphogenetic processes and discuss what aspects of apicobasal crosstalk may represent widespread phenomena and which ones are used to build subsets of specialised compartments.

scholarly journals Electric field-directed cell shape changes, displacement, and cytoskeletal reorganization are calcium dependent.

1988 ◽  
Vol 106 (6) ◽  
pp. 2067-2075 ◽  
Author(s):  
E K Onuma ◽  
S W Hui
Keyword(s):  
Electric Field ◽  
Calcium Channel ◽  
Calcium Channel Blocker ◽  
Cell Shape ◽  
Channel Blocker ◽  
Stress Fiber ◽  
Calmodulin Antagonist ◽  
Calcium Dependent ◽  
Cell Shape Changes ◽  
Shape Changes

C3H/10T1/2 mouse embryo fibroblasts were stimulated by a steady electric field ranging up to 10 V/cm. Some cells elongated and aligned perpendicular to the field direction. A preferential positional shift toward the cathode was observed which was inhibited by the calcium channel blocker D-600 and the calmodulin antagonist trifluoperazine. Rhodaminephalloidin labeling of actin filaments revealed a field-induced disorganization of the stress fiber pattern, which was reduced when stimulation was conducted in calcium-depleted buffer or in buffer containing calcium antagonist CoCl2, calcium channel blocker D-600, or calmodulin antagonist trifluoperazine. Treatment with calcium ionophore A23187 had similar effects, except that the presence of D-600 did not reduce the stress fiber disruption. The calcium-sensitive photoprotein aequorin was used to monitor changes in intracellular-free calcium. Electric stimulation caused an increase of calcium to the micromolar range. This increase was inhibited by calcium-depleted buffer or by CoCl2, and was reduced by D-600. A calcium-dependent mechanism is proposed to explain the observed field-directed cell shape changes, preferential orientation, and displacement.

Organization of the Pellicle and the Muciferous Glands in Euglena Gracilis

1970 ◽  
Vol 28 ◽  
pp. 104-105
Author(s):  
Hilton H. Mollenhauer ◽  
W. Evans
Keyword(s):  
Plasma Membrane ◽  
Euglena Gracilis ◽  
Complex Forms ◽  
Secondary Periodicity

The pellicular structure of Euglena gracilis consists of a series of relatively rigid strips (Fig. 1) composed of ridges and grooves which are helically oriented along the cell and which fuse together into a common junction at either end of the cell. The strips are predominantly protein and consist in part of a series of fibers about 50 Å in diameter spaced about 85 Å apart and with a secondary periodicity of about 450 Å. Microtubules are also present below each strip (Fig. 1) and are often considered as part of the pellicular complex. In addition, there may be another fibrous component near the base of the pellicle which has not yet been very well defined.The pellicular complex lies underneath the plasma membrane and entirely within the cell (Fig. 1). Each strip of the complex forms an overlapping junction with the adjacent strip along one side of each groove (Fig. 1), in such a way that a certain amount of sideways movement is possible between one strip and the next.

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