Restoration of movement and apical growth in the angiosperm pollen tube following cytochalasin-induced paralysis

1991 ◽  
Vol 331 (1260) ◽  
pp. 225-235 ◽  
Keyword(s):  
Actin Cytoskeleton ◽  
Vegetative Cells ◽  
Cytoplasmic Inclusions ◽  
Essentially Normal ◽  
Narcissus Pseudonarcissus ◽  
Partial Dissociation ◽  
Actin Fibrils ◽  
Angiosperm Pollen ◽  
Generative Cells ◽  
Rapid Contraction

Cytochalasin D (CD) at 5 pg ml- 1 arrested growth and vectorial movement in pollen tubes of Narcissus pseudonarcissus and Endymion nonscriptus and caused the mainly longitudinally oriented actin fibrils in the vegetative cells to coalesce and form massive, more randomly oriented, cables. As extension growth was arrested, the tubes formed apical bulbs and abnormal wall thickenings. During recovery from a 10 min treatment period in E. nonscriptus , an essentially normal fibril system was reconstituted by partial dissociation of the thick cables formed during the exposure to CD. As this progressed movement was restored in the vegetative cells. Some 80 % of the blocked tubes initiated new growing points, either by producing randomly oriented swellings in sites where the wall was thinner, or by erosion and penetration of thicker zones. Contrary to expectation, the sites of the prospective growing points were not indicated in advance by any special disposition of the actin cytoskeleton. With the transition to cylindrical growth in the secondary tubes the standard stratification of the tube wall reappeared, with outer pectocellulosic and inner callosic layers. Normal movement pathways were established concomitantly, together with the apical zonation of organelles and other cytoplasmic inclusions characteristic of the extending tube. CD-treatment brought about rapid contraction of the vegetative nuclei with the loss of the elastic extensions of the nuclear envelopes. The extended form was resumed as the actin cytoskeleton was restored during recovery, and vegetative nuclei and generative cells moved into the secondary tubes where they continued to track the apex as in the normal tube.

scholarly journals Myosin associated with the surfaces of organelles, vegetative nuclei and generative cells in angiosperm pollen grains and tubes

1989 ◽  
Vol 94 (2) ◽  
pp. 319-325
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON
Keyword(s):  
Pollen Tube ◽  
Pollen Grains ◽  
Giant Cells ◽  
Pollen Tubes ◽  
Microfilament Bundles ◽  
Hyacinthus Orientalis ◽  
Actin Fibrils ◽  
Angiosperm Pollen ◽  
Muscle Myosin ◽  
Generative Cells

Myosin, detected by immunofluorescence using an antibody to bovine skeletal and smooth muscle myosin, has been localised on individual identifiable organelles from the grasses Alopecurus pratensis and Secale cereale, and on the surfaces of vegetative nuclei and generative cells from pollen and pollen tubes of Hyacinthus orientalis and Helleborus foetidus. Taken in conjunction with recent evidence showing that the growing pollen tube contains an actin cytoskeleton consisting of numerous mainly longitudinally oriented microfilament bundles, and that isolated pollen-tube organelles show ATP-dependent movement along the actin bundles of the giant cells of the characeous algae, this finding suggests that an actomyosin motility system is present in pollen tubes, and indicates that the movements of the different classes of inclusions are driven by interaction of the surface myosin with the actin fibrils at the zones of contact.

Conformation and movement of the vegetative nucleus of the angiosperm pollen tube: association with the actin cytoskeleton

1989 ◽  
Vol 93 (2) ◽  
pp. 299-308
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON
Keyword(s):  
Pollen Tube ◽  
Actin Cytoskeleton ◽  
Nuclear Envelope ◽  
Vegetative Cell ◽  
Cytochalasin D ◽  
Vegetative Nucleus ◽  
Continuous Change ◽  
Cytoplasmic Bodies ◽  
Angiosperm Pollen ◽  
Rapid Contraction

Actin is present in the cytoplasm of the vegetative cell of angiosperm pollens in numerous fusiform, spiculate or toroidal bodies, and also as a sheath enveloping the vegetative nucleus. During activation following hydration, the compact cytoplasmic bodies are translated into skeins of extended fibrils, and circulatory movements begin in the cytoplasm. Throughout this period the vegetative nucleus, with fibrillar actin now associated with the surface, undergoes a continuous change of shape. In the extending tube following germination the actin cytoskeleton consists of numerous mainly longitudinally oriented fibrils. After entry into the tube the vegetative nucleus remains associated with the fibrils, usually extending greatly in length and developing attenuated, often pointed extensions. The observed conformations, which change continuously, suggest that varying local tensions are applied to the vegetative nucleus during passage through the tube. Cytochalasin D breaks up the actin fibril system and brings about a rapid contraction of the nucleus, at the same time eliminating the elastic extensions of the nuclear envelope. Nuclei isolated physically from unfixed tubes also contract in length as the fibrillar components of the cytoskeleton are detached. These findings indicate that the movement of the vegetative nucleus depends on local associations of the nuclear envelope with the actin cytoskeleton of the vegetative cell.

scholarly journals The actin cytoskeleton and integrin expression in the recovery of cell adhesion after oxidant stress to a proximal tubule cell line (JTC-12).

1998 ◽  
Vol 9 (10) ◽  
pp. 1787-1797
Author(s):  
S Nigam ◽  
C E Weston ◽  
C H Liu ◽  
E E Simon
Keyword(s):  
Cell Adhesion ◽  
Actin Cytoskeleton ◽  
Proximal Tubule ◽  
Cell Line ◽  
Oxidant Stress ◽  
Proximal Tubule Cell ◽  
Integrin Expression ◽  
Tubule Cell ◽  
Essentially Normal ◽  
Atp Levels

This study examines the role of the actin cytoskeleton and integrin expression in the recovery of cell adhesion in the proximal tubule cell line JTC-12 after peroxide injury. The cells were exposed to 10, 20, or 50 mM hydrogen peroxide for 10 min and then allowed to recover. Viability measurements by trypan blue exclusion confirmed that the injury was largely nonlethal with 85% viability at 1 h even at 50 mM peroxide. ATP levels fell immediately after the peroxide incubation in all groups to approximately 10% of normal, but already showed some recovery by 1 h and full recovery in the 10 and 20 mM groups by 24 h. Cell adhesion to extracellular matrix immediately after injury was depressed at 20 and 50 mM peroxide, but by 12 h was abnormal only at 50 mM peroxide and at 24 h was essentially normal at all peroxide concentrations. Immediately after exposure to 10 mM peroxide, there were subtle abnormalities in the actin cytoskeleton (thickening of fibrils) as assessed by phalloidin staining, with more pronounced effects at 20 and 50 mM. At 1 h, many cells showed collapse of the actin cytoskeleton to the periphery. There was some recovery at 4 h; by 12 h, the actin cytoskeleton showed further recovery, although was still abnormal (coarsened microfilaments), especially at 20 and 50 mM peroxide. By 24 h, the actin cytoskeleton showed only subtle coarsening. Integrin surface expression was assessed by flow cytometry. The alpha6 subunit on cells exposed to 20 mM peroxide was unchanged at 1 h and 4 h, but by 12 h had increased to 118.5+/-4.5% and by 24 h to 146+/-13.4% of control levels. The expression of the beta1 and alphaVbeta3 integrins remained unchanged. Thus, despite coarsening of the actin cytoskeleton and depressed ATP levels, cell adhesion recovered from oxidant stress. Abnormal cell adhesion after injury was not a consequence of a decrease in integrin expression, and recovery of cell adhesion was not a consequence of the modest and selective increase in integrin expression.

scholarly journals Shared and Unique Roles of Cap23 and Gap43 in Actin Regulation, Neurite Outgrowth, and Anatomical Plasticity

2000 ◽  
Vol 149 (7) ◽  
pp. 1443-1454 ◽  
Author(s):  
Dunja Frey ◽  
Thorsten Laux ◽  
Lan Xu ◽  
Corinna Schneider ◽  
Pico Caroni
Keyword(s):  
Actin Cytoskeleton ◽  
Neurite Outgrowth ◽  
Critical Role ◽  
Brain Structures ◽  
Calmodulin Binding ◽  
Essentially Normal ◽  
Anatomical Plasticity ◽  
Nerve Sprouting

CAP23 is a major cortical cytoskeleton–associated and calmodulin binding protein that is widely and abundantly expressed during development, maintained in selected brain structures in the adult, and reinduced during nerve regeneration. Overexpression of CAP23 in adult neurons of transgenic mice promotes nerve sprouting, but the role of this protein in process outgrowth was not clear. Here, we show that CAP23 is functionally related to GAP43, and plays a critical role to regulate nerve sprouting and the actin cytoskeleton. Knockout mice lacking CAP23 exhibited a pronounced and complex phenotype, including a defect to produce stimulus-induced nerve sprouting at the adult neuromuscular junction. This sprouting deficit was rescued by transgenic overexpression of either CAP23 or GAP43 in adult motoneurons. Knockin mice expressing GAP43 instead of CAP23 were essentially normal, indicating that, although these proteins do not share homologous sequences, GAP43 can functionally substitute for CAP23 in vivo. Cultured sensory neurons lacking CAP23 exhibited striking alterations in neurite outgrowth that were phenocopied by low doses of cytochalasin D. A detailed analysis of such cultures revealed common and unique functions of CAP23 and GAP43 on the actin cytoskeleton and neurite outgrowth. The results provide compelling experimental evidence for the notion that CAP23 and GAP43 are functionally related intrinsic determinants of anatomical plasticity, and suggest that these proteins function by locally promoting subplasmalemmal actin cytoskeleton accumulation.

Cytoskeletal Elements, Cell Shaping and Movement in the Angiosperm Pollen Tube

1988 ◽  
Vol 91 (1) ◽  
pp. 49-60 ◽  
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON ◽  
M. CRESTI ◽  
A. TIEZZI ◽  
A. MOSCATELLI
Keyword(s):  
Pollen Tube ◽  
Shape Change ◽  
Generative Cell ◽  
Vegetative Nucleus ◽  
Microtubule Cytoskeleton ◽  
Tube Shape ◽  
Galanthus Nivalis ◽  
Angiosperm Pollen ◽  
Cytoskeletal Elements ◽  
Generative Cells

The ellipsoidal generative cell of the pollen grain of Endymion nonscriptus usually elongates further following germination and entry into the tube, producing attenuated extensions the forward one of which may reach into the vicinity of the vegetative nucleus. This shape change is accompanied by the stretching of the microtubule cytoskeleton of the cell, identified in the present work by immunofluorescence using monoclonal antibodies to tubulin. Complementary observations of living generative cells of Iris pseudacorus showed that they undergo slow undulatory movements accompanied by variation in shape and length during passage through the tube. Such changes must presumably be accompanied by modifications of the microtubule cytoskeleton. Colchicine at 1 mM eliminated microtubules from tubes and most generative cells of E. nonscriptus, but did not radically affect pollen-tube shape or extension growth, nor arrest the movements of the vegetative nucleus and generative cell into and through the tube. Generative cells in colchicinetreated pollen of Galanthus nivalis rounded up and failed to undergo the usual changes in shape during passage through the tube. Secondary consequences were changes in precedence in movement through the tube, and a greater dispersal along its length. On the assumption that no other cytoskeletal elements remain to be discovered, it seems likely that microfilaments rather than microtubules provide the motive force for movement in the tube, although the latter are involved in shaping the generative cell and adapting it to its passage.

scholarly journals Ultrastructure and Differentiation in Chara Sp.I. Vegetative Cells

1967 ◽  
Vol 20 (3) ◽  
pp. 539 ◽  
Author(s):  
JD Pickett-Heaps
Keyword(s):  
Endoplasmic Reticulum ◽  
Cytoplasmic Streaming ◽  
Plant Cells ◽  
Membrane Systems ◽  
Close Apposition ◽  
Vegetative Cells ◽  
Cytoplasmic Inclusions ◽  
Golgi Bodies ◽  
And Function ◽  
Vacuolated Cells

The ultrastructure of young growing cells of Ohara is described. The cells showed many features typical of plant cells. The nuclei of larger cells invariably contained groups of close�packed, heavily staining microtubular elements. Typical wall microtubules were always found, and large internodal cells contained filaments possibly involved in cytoplasmic streaming. Vacuolation in young internodes apparently commenced by extensive dilation of elements of the endoplasmic reticulum. In other cells, close apposition of endoplasmic reticulum to cytoplasmic inclusions indicated possible secretion of material into the organelles had been occurring. Golgi bodies with intercisternal elements were often grouped together, sometimes with interconnected cisternae. Isolated reticulate membrane systems, similar to those found at the reticulate face of golgi bodies, were sometimes seen in vacuolated cells. The golgi bodies might have been involved in vacuolation; they were also seen in association with coated vesicles that appeared to be involved in wall deposition. A large number of different cytoplasmic inclusions were found, whose nature and function is obscure. These sometimes contained crystal.like bodies.

Electron Microscopy of Fibroblasts from Myotonic Muscular Dystrophy Patients

1981 ◽  
Vol 39 ◽  
pp. 498-499
Author(s):  
S. E. Miller ◽  
G. B. Hartwig ◽  
R. A. Nielsen ◽  
A. P. Frost ◽  
A. D. Roses
Keyword(s):  
Electron Microscopy ◽  
Muscular Dystrophy ◽  
Genetic Diseases ◽  
Skin Fibroblasts ◽  
Inborn Errors ◽  
Cytoplasmic Inclusions ◽  
Cultured Skin ◽  
Myotonic Muscular Dystrophy ◽  
Glycosaminoglycan Metabolism

Many genetic diseases can be demonstrated in skin cells cultured in vitro from patients with inborn errors of metabolism. Since myotonic muscular dystrophy (MMD) affects many organs other than muscle, it seems likely that this defect also might be expressed in fibroblasts. Detection of an alteration in cultured skin fibroblasts from patients would provide a valuable tool in the study of the disease as it would present a readily accessible and controllable system for examination. Furthermore, fibroblast expression would allow diagnosis of fetal and presumptomatic cases. An unusual staining pattern of MMD cultured skin fibroblasts as seen by light microscopy, namely, an increase in alcianophilia and metachromasia, has been reported; both these techniques suggest an altered glycosaminoglycan metabolism An altered growth pattern has also been described. One reference on cultured skin fibroblasts from a different dystrophy (Duchenne Muscular Dystrophy) reports increased cytoplasmic inclusions seen by electron microscopy. Also, ultrastructural alterations have been reported in muscle and thalamus biopsies from MMD patients, but no electron microscopical data is available on MMD cultured skin fibroblasts.

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