scholarly journals EXOCYTOSIS OF LATEX BEADS DURING THE ENCYSTMENT OF ACANTHAMOEBA

1972 ◽  
Vol 52 (1) ◽  
pp. 117-130 ◽  
Author(s):  
James R. Stewart ◽  
Robert A. Weisman
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Cyst Wall ◽  
Actinomycin D ◽  
Acanthamoeba Castellanii ◽  
Ultrastructural Analysis ◽  
Synthetase Activity ◽  
Wall Formation ◽  
Latex Beads ◽  
In Cells

Cells of Acanthamoeba castellanii (Neff) are known to form mature cysts characterized by a cellulose-containing cell wall when transferred to a nonnutrient medium. Amebas which engulfed latex beads before encystment formed mature cysts essentially devoid of bead material. The encystment of bead-containing cells appeared to be similar to that of control cells since no important differences between the two were observed with respect to cellular levels of glycogen or protein, cellulose synthetase activity, the amount of cyst wall polysaccharide formed, or the percentage of cysts formed. Actinomycin D and cycloheximide inhibited encystment as well as bead expulsion. Ultrastructural analysis revealed that the beads, which initially were contained in phagocytic vesicles, were released from the cell by fusion of vesicular membranes with the plasma membrane. Exocytosis was observed in cells after 3 hr of encystment, with most of the beads being lost before cyst wall formation. Each bead-containing vesicle involved in expulsion was conspicuously demarcated by an area of concentrated cytoplasm, which was more homogeneously granular than the surrounding cytoplasm. Beads were not observed in the cytoplasm of mature cysts but were occasionally found in the cyst wall.

scholarly journals Ultrastructural Analysis of Cell Wall Formation and Cell Division of Soybean Protoplasts.

1993 ◽  
Vol 62 (3) ◽  
pp. 429-437
Author(s):  
Salak PHANSIRI ◽  
Hiroshi MIYAKE ◽  
Eizo MAEDA ◽  
Takeshi TANIGUCHI
Keyword(s):  
Cell Wall ◽  
Cell Division ◽  
Ultrastructural Analysis ◽  
Cell Wall Formation ◽  
Wall Formation

scholarly journals LRX Proteins play a crucial role in pollen grain and pollen tube cell wall development

2017 ◽  
Author(s):  
Tohnyui Ndinyanka Fabrice ◽  
Hannes Vogler ◽  
Christian Draeger ◽  
Gautam Munglani ◽  
Shibu Gupta ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Pollen Tube ◽  
Protein Interactions ◽  
Molecular Techniques ◽  
Fine Tuning ◽  
Cell Wall Formation ◽  
Leucine Rich Repeat ◽  
Biophysical Parameters ◽  
Wall Formation

AbstractLeucine-rich repeat extensins (LRXs) are chimeric proteins containing an N-terminal leucine-rich repeat (LRR) and a C-terminal extensin domain. LRXs are involved in cell wall formation in vegetative tissues and required for plant growth. However, the nature of their role in these cellular processes remains to be elucidated. Here, we used a combination of molecular techniques, light microscopy, and transmission electron microscopy to characterize mutants of pollen-expressed LRXs in Arabidopsis thaliana. Mutations in multiple pollen-expressed lrx genes causes severe defects in pollen germination and pollen tube (PT) growth, resulting in a reduced seed set. Physiological experiments demonstrate that manipulating Ca2+ availability partially suppresses the PT growth defects, suggesting that LRX proteins influence Ca2+-related processes. Furthermore, we show that LRX protein localizes to the cell wall, and its LRR-domain (which likely mediates protein-protein interactions) is associated with the plasma membrane. Mechanical analyses by cellular force microscopy and finite element method-based modelling revealed significant changes in the material properties of the cell wall and the fine-tuning of cellular biophysical parameters in the mutants compared to the wild type. The results indicate that LRX proteins might play a role in cell wall-plasma membrane communication, influencing cell wall formation and cellular mechanics.

scholarly journals 1727. Candida albicans Phosphatidylinositol-(4,5)-Bisphosphate (PIP2) Directs Aberrant Cytokinesis and Septation in Response to Echinocandins, Which Correlates with Fungicidal Activity and Attenuated Virulence

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S633-S633
Author(s):  
Hassan Badrane ◽  
Minh-Hong Nguyen ◽  
Cornelius J Clancy
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Live Cell Imaging ◽  
Plasma Membranes ◽  
Cell Imaging ◽  
Fungicidal Activity ◽  
Wild Type ◽  
Cell Wall Integrity Pathway ◽  
Dividing Cells ◽  
In Cells

Abstract Background We previously showed that highly dynamic PIP2, septin, and PKC-Mkc1 cell wall integrity pathway responses correlate with echinocandin activity against C. albicans and attenuated virulence during invasive candidiasis. Our objectives were to determine whether PIP2 dysregulation in response to an echinocandin results in aberrant localization of the septation and cytokinesis apparatus, and to quantitate aberrant localization. Methods Live cell imaging (LCI) was performed for 3 hours (Nikon A1 confocal microscope, NIS Elements software; Tokyo) on C. albicans irs4 mutant and wild-type SC5314 expressing fluorescently labeled PIP2 and Cdc10 (septin), Act1 (actin), or Myo1 (myosin). Results C. albicans irs4, in which PIP2 5’-phosphatase is disrupted, mislocalizes PIP2 and septins, and over-activates the PKC-Mkc1 pathway in a manner similar to echinocandin-exposed C. albicans SC5314. LCI revealed that PIP2 co-localized with Act1 and Myo1 at aberrant sites in C. albicans irs4, similar to PIP2-Cdc10 co-localization. 83% of co-localizing patches were in cells undergoing active cytokinesis. 78% of patches were at sites of cytokinesis, which reflected both normal budding and abnormal, wide-necked budding; 5% of patches localized to aberrant plasma membrane sites during cytokinesis. 17% of co-localizing patches were in cells that were not undergoing active cytokinesis. 6% of patches were at old cytokinesis sites; 11% of patches were at aberrant plasma membrane sites. Similar PIP2-septin-actin-myosin dysregulation was observed in C. albicans SC5314 immediately upon 4x MIC caspofungin exposure (Figure; videos). Conclusion Dysregulated C. albicans PIP2 recruits the septation and cytokinesis apparatus, including septins, actin, and myosin, to sites of incomplete cytokinesis at bud necks and to sites of aberrant, ectopic septation in plasma membranes of both dividing and non-dividing cells. Our data support a model in which a dysregulated PIP2 response is triggered immediately upon echinocandin exposure, over-activates the PKC-Mkc-1 pathway, and correlates with the extent of fungicidal activity and attenuated virulence. PIP2-septation-cytokinesis dysregulation is likely to lead to C. albicans death by promoting cell lysis, or selecting cells to undergo apoptosis. Disclosures All authors: No reported disclosures.

scholarly journals Genetical and structural analyses of cell-wall formation in Chlamydomonas reinhardi

1971 ◽  
Vol 17 (1) ◽  
pp. 33-43 ◽  
Author(s):  
D. Roy Davies ◽  
A. Plaskitt
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Single Gene ◽  
Three Dimensional ◽  
Cell Wall Formation ◽  
Wild Type ◽  
Nuclear Level ◽  
Wall Formation ◽  
Cell Wall Biogenesis ◽  
Mutant Strains

SUMMARYFifteen mutant strains of Chlamydomonas reinhardi were isolated which showed defects in some aspect of the process of cell-wall formation. Genetic analyses indicated that most of the mutations were due to single gene changes; two were anomalous in that non-Mendelian segregations were obtained on crossing with other genotypes, and on selfing they frequently gave rise to wild-type phenotypes.Occasional somatic revertants were also obtained from these two strains. On the basis of these analyses it is suggested that there are two levels of control operating in the process of cell wall biogenesis - one concerned with subunit production at the nuclear level and another, possibly concerned with three-dimensional organization, at another level. Electron-microscope analyses of the different mutants showed the mutants to be divided into three main categories: those in which the wall was formed but was not attached to the plasma membrane, those in which the wall was attached to the membrane, and those in which very little wall was formed. In the last class in particular, vesicles containing wall precursors were clearly visible, and were shed through the plasma membrane into the medium.

Multivesicular structures and cell wall growth

1969 ◽  
Vol 47 (12) ◽  
pp. 1873-1877 ◽  
Author(s):  
L. C. Fowke ◽  
George Setterfield
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Physiological State ◽  
Plant Cells ◽  
Wall Material ◽  
Golgi Bodies ◽  
Wall Growth ◽  
Cell Wall Deposition ◽  
Applied Auxin ◽  
In Cells

Applied auxin caused cells of artichoke tuber slices to expand and deposit significant amounts of new wall material while cells in slices held on water remained essentially inert in both respects. Cells in all physiological treatments showed multivesicular structures at the plasma membrane (plasmalemmasomes, lomasomes), within the cytoplasm and within the central vacuoles. The number of plasmalemmasomes was considerably greater in cells not depositing wall than in cells treated with auxin to stimulate wall synthesis. Multivesicular structures showed no relation to Golgi bodies, which increase in number and apparent activity in response to auxin treatment. It is concluded that plasmalemmasomes are not involved in cell wall deposition. Multivesicular structures in plant cells could have several origins and it is suggested that some may represent artifactual reorganization of plasmalemma and tonoplast membranes during cytological processing. Such reorganization would presumably be sensitive to the physiological state of the tissue.

Lomasomes and vesicles in Poria monticola

1971 ◽  
Vol 49 (12) ◽  
pp. 2075-2079 ◽  
Author(s):  
J. A. Brushaber ◽  
S. F. Jenkins Jr.
Keyword(s):  
Plasma Membrane ◽  
Membrane Structure ◽  
Structure Characteristic ◽  
Wall Formation ◽  
Pinocytotic Vesicles ◽  
True Structure ◽  
Tubular Bodies ◽  
In Cells

A study of the vesicular and tubular bodies observed in cells of Poria monticola was done with particular regard to their form, origin, and membrane structure. The membranes of lomasomes and pinocytotic vesicles display the sometimes asymmetric, distinctly trilaminar structure characteristic of the plasma membrane. Lomasomes are abundant and vary in appearance depending upon the method of fixation used. Nonlamellar associations of vesicles and short tubules probably represent the true structure of lomasomes in this organism. These lomasomes originate from the plasma membrane and do not appear to be associated exclusively with wall formation.

Turnover of Plasma Membrane During Phagocytosis

1972 ◽  
Vol 11 (2) ◽  
pp. 569-579
Author(s):  
R. J. GOODALL ◽  
Y. F. LAI ◽  
J. E. THOMPSON
Keyword(s):  
Plasma Membrane ◽  
Cytoplasmic Membrane ◽  
De Novo ◽  
Surface Membrane ◽  
Acanthamoeba Castellanii ◽  
De Novo Synthesis ◽  
Cellular Membranes ◽  
Latex Beads ◽  
Specific Radio ◽  
Preferential Synthesis

Levels of radioactive glycine and glycerol incorporated into the plasma membrane of Acanthamoeba castellanii during phagocytosis were determined in order to elucidate how surface membrane expended during this process is replaced. The amoebae were allowed to ingest latex beads in the presence of the labelled membrane precursors and plasma membrane was then isolated and analysed for the presence of radioactivity. The isolated membrane fragments were found to be quite highly labelled. In order to ascertain whether this represented preferential synthesis of plasma membrane in response to phagocytosis, the specific radio-activities of the isolated membrane fractions were compared with those of corresponding particulate homogenates, which were composites of all cellular membranes. Enrichment values calculated in this manner proved to be essentially similar for both phagocytosing and non-phagocytosing amoebae. This indicates that de novo synthesis of plasma membrane is not essential for phagocytosis and in turn suggests that pre-existing cytoplasmic membrane is used to replace surface membrane consumed during ingestion. Presumably the incorporation of membrane precursors that was observed represents molecular turnover that occurs irrespective of phagocytosis.

Microanatomy of the Periplasm of Bacillus Licheniformis

1971 ◽  
Vol 29 ◽  
pp. 262-263
Author(s):  
B.K. Ghosh
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Bacillus Licheniformis ◽  
External Environment ◽  
Permeability Barrier ◽  
Periplasmic Space ◽  
Modified Technique ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

Periplasm of bacteria is the space outside the permeability barrier of plasma membrane but enclosed by the cell wall. The contents of this special milieu exterior could be regulated by the plasma membrane from the internal, and by the cell wall from the external environment of the cell. Unlike the gram-negative organism, the presence of this space in gram-positive bacteria is still controversial because it cannot be clearly demonstrated. We have shown the importance of some periplasmic bodies in the secretion of penicillinase from Bacillus licheniformis.In negatively stained specimens prepared by a modified technique (Figs. 1 and 2), periplasmic space (PS) contained two kinds of structures: (i) fibrils (F, 100 Å) running perpendicular to the cell wall from the protoplast and (ii) an array of vesicles of various sizes (V), which seem to have evaginated from the protoplast.

Effect of Some Metabolic Inhibitors on Vinblastine-Induced Ribosomal-Granular Material Complexes

1971 ◽  
Vol 29 ◽  
pp. 548-549
Author(s):  
Awtar Krishan ◽  
Dora Hsu
Keyword(s):  
Granular Material ◽  
Rna Synthesis ◽  
Culture Medium ◽  
Actinomycin D ◽  
Metabolic Inhibitors ◽  
Protein And Rna Synthesis ◽  
Apparent Reduction ◽  
Plant Alkaloids ◽  
In Cells

Cells exposed to antitumor plant alkaloids, vinblastine and vincristine sulfate have large proteinacious crystals and complexes of ribosomes, helical polyribosomes and electron-dense granular material (ribosomal complexes) in their cytoplasm, Binding of H3-colchicine by the in vivo crystals shows that they contain microtubular proteins. Association of ribosomal complexes with the crystals suggests that these structures may be interrelated.In the present study cultured human leukemic lymphoblasts (CCRF-CEM), were incubated with protein and RNA-synthesis inhibitors, p. fluorophenylalanine, puromycin, cycloheximide or actinomycin-D before the addition of crystal-inducing doses of vinblastine to the culture medium. None of these compounds could completely prevent the formation of the ribosomal complexes or the crystals. However, in cells pre-incubated with puromycin, cycloheximide, or actinomycin-D, a reduction in the number and size of the ribosomal complexes was seen. Large helical polyribosomes were absent in the ribosomal complexes of cells treated with puromycin, while in cells exposed to cycloheximide, there was an apparent reduction in the number of ribosomes associated with the ribosomal complexes (Fig. 2).

Enrichment of vitronectin- and fibronectin-like proteins in NaCI-adapted plant cells and evidence for their involvement in plasma membrane-cell wall adhesion

1993 ◽  
Vol 3 (5) ◽  
pp. 637-646 ◽  
Author(s):  
Jian-Kang Zhu ◽  
Jun Shi ◽  
Utpal Singh ◽  
Sarah E. Wyatt ◽  
Ray A. Bressan ◽  
...  
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Plant Cells ◽  
Membrane Cell
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