Effects of Hormones on the Polysaccharide-Synthesizing Membrane Systems of Lettuce Pith

1974 ◽  
Vol 16 (2) ◽  
pp. 433-443
Author(s):  
K. WRIGHT ◽  
D. J. BOWLES
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Walls ◽  
Membrane Systems ◽  
Radioactive Precursor

Changes have been induced in the polysaccharides laid down in the cell walls of lettuce pith by administration of the hormones auxin and zeatin. This polysaccharide derives from the membrane systems of the cells and radioactive precursor has been used to follow the accompanying changes which occurred in the polysaccharide contained within isolated Golgi and endoplasmic reticulum fractions. Zeatin-induced division and differentiation was accompanied by up to 12-fold increases in the amount of radioactivity in polysaccharide of isolated membrane fractions, and the pattern of distribution of label between the sugars of this polysaccharide was qualitatively different in the presence of zeatin. The change in this pattern was evident in the Golgi fraction at an earlier stage in the induction of the response than that in the endoplasmic reticulum.

scholarly journals The Lamellar Systems of Cytoplasmic Membranes in Dividing Spermatogenic Cells of Drosophila virilis

1960 ◽  
Vol 7 (3) ◽  
pp. 433-441 ◽  
Author(s):  
Susumu Ito
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Complex ◽  
Light And Electron Microscopy ◽  
Primary Spermatocyte ◽  
Drosophila Virilis ◽  
Spermatogenic Cells ◽  
Membrane Systems ◽  
Cytoplasmic Membranes ◽  
Pas Reaction ◽  
Staining Methods

Spermatogenic cells of Drosophila virilis were studied by light and electron microscopy. The persistence of a "nuclear wall" during the meiotic divisions has been reported by a number of early cytologists, but this interpretation has been a subject of debate. Electron micrographs of dividing spermatocytes reveal the presence of multiple layers of paired membranes surrounding the nuclear region. These lamellar membrane systems are not typical of the nuclear envelope, but were interpreted as such by light microscopists. The membranes constituting a pair are separated by an interspace of ∼ 100 A and successive pairs are 200 to 400 A apart. These spacings are similar but not identical to those found in the lamellar systems of the Golgi complex. The cisternae of the endoplasmic reticulum in this material are devoid of attached ribonucleoprotein particles, are more precisely ordered than in vertebrate cells, and show a uniform, narrow intracisternal space of ∼ 100 A. The conspicuous asters appear to be made up of similar paired membranes radiating from the centriolar region. The primary spermatocyte has numerous dictyosomes and a well developed endoplasmic reticulum in cisternal form, but no typical Golgi complex or endoplasmic reticulum is found during the meiotic division stages of metaphase to telophase. Evidence is presented that these cytoplasmic organelles contribute to the formation of the extensive lamellar systems that appear during meiosis. The results of the Golgi silver staining methods and staining tests for phospholipids, basophilia, and the PAS reaction, indicate that the lamellar arrays of membranes present during meiosis are indistinguishable from the Golgi complex in their tinctorial properties.

Ultrastructural comparisons of fungus hyphal cells using frozen-etched replicas and thin sections of the fungus Pyrenochaeta terrestris

1968 ◽  
Vol 14 (3) ◽  
pp. 205-210 ◽  
Author(s):  
W. M. Hess
Keyword(s):  
Electron Scattering ◽  
Cell Walls ◽  
Sole Carbon Source ◽  
Membrane Systems ◽  
Thin Sections ◽  
Fixed Membrane ◽  
Pyrenochaeta Terrestris ◽  
Freeze Etching ◽  
Fixed Cell ◽  
Etched Membrane

The ultrastructure of P. terrestris hyphal cells was investigated to compare frozen-etched replicas with chemically fixed thin sections. The fungus used in this study uses glycerol as a sole carbon source and survives the freezing procedures necessary for freeze-etching; thus frozen-etched replicas reflect the living state.Frozen-etched membrane systems have particles of various sizes and concentrations and have a smooth appearance as contrasted to chemically fixed membrane systems, which have particles difficult to distinguish and somewhat irregular membrane systems. Frozen-etched cell walls are seen to contain particles, and microfibrillar orientation is evident in older cell walls, whereas substructure is not evident in chemically fixed cell walls, although secretion products of the fungus accumulate on cell surfaces.Chemically fixed ground cytoplasm has ribosomes and areas of high- and low-electron scattering which are not seen with freeze-etching. Cells fixed in glutaraldehyde–acrolein–OsO4 more nearly resemble frozen-etched cells than cells fixed in potassium permanganate.

The polypeptides of rat liver nuclear envelope. II. Comparison of rat liver nuclear membrane polypeptides with those of the rough endoplasmic reticulum

1980 ◽  
Vol 43 (1) ◽  
pp. 269-277
Author(s):  
J.C. Richardson ◽  
A.H. Maddy
Keyword(s):  
Endoplasmic Reticulum ◽  
Rat Liver ◽  
Rough Endoplasmic Reticulum ◽  
Nuclear Membrane ◽  
Relative Proportion ◽  
Membrane System ◽  
Membrane Systems ◽  
Nuclear Membranes ◽  
Cytoplasmic Surface ◽  
Triton X

Nuclear envelopes are separated into pore-lamina and membrane sub-fractions by extraction in 2.0% Triton X-100 followed by pelleting of the pore-laminae. The polypeptides of these subfractions are then compared with those from isolated rough endoplasmic reticulum. The dispositions of individual polypeptides in the cytoplasmic surface of nuclear envelopes and rought endoplasmic reticulum were studied by lactoperoxidase-catalysed iodination. These studies show that although the nuclear membranes exhibit several homologies with the Triton-soluble polypeptides of the rough endoplasmic reticulum the relative proportion of individual polypeptides within the two systems are very largely different. The cytoplasmic surfaces of the 2 membrane systems show only 2 obvious homologies at 105 000 and 15 000 mol. wt and the overall impression is that, at least in rat liver, the outer nuclear membrane is very substantially differentiated from rough endoplasmic reticulum. It is concluded that the nuclear membranes may not be regarded as a mere continuum of the endoplasmic reticulum, but should be seen as a highly specialized membrane system in their own right.

Ultrastructural Observations of Cell Wall Regeneration Around Isolated Tobacco Protoplasts

1974 ◽  
Vol 14 (2) ◽  
pp. 439-449
Author(s):  
J. BURGESS ◽  
E. N. FLEMING
Keyword(s):  
Electron Microscopy ◽  
Heavy Metal ◽  
Endoplasmic Reticulum ◽  
Cell Wall ◽  
Cell Wall Regeneration ◽  
Membrane Systems ◽  
Tobacco Protoplasts ◽  
Wall Formation ◽  
Wall Regeneration ◽  
Wall Growth

The process of cell wall regeneration around cultured protoplasts isolated from tobacco mesophyll has been examined by electron microscopy. The initially formed wall contains 2 components which stain with conventional heavy metal stains. The first consists of un-branched fibres, at first oriented at right angles to the plasmalemma surface. As wall growth proceeds the fibres lengthen and assume an orientation parallel to the plasmalemma. It seems probable that this component is cellulose. The second component of the wall is more amorphous and more densely stained. It is most frequently seen in situations where leaching of materials into the medium would be expected to be minimal. The endoplasmic reticulum and the plasmalemma are the only membrane systems which appear to contribute towards wall formation. No pattern of structure has been detected to explain the orientation or method of synthesis of the microfibrillar part of the wall.

CHANGES IN CELL FINE STRUCTURE OF LIMA BEAN AXES DURING EARLY GERMINATION

1966 ◽  
Vol 44 (3) ◽  
pp. 331-340 ◽  
Author(s):  
Shimon Klein ◽  
Yehuda Ben-Shaul
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Cell Walls ◽  
Lipid Droplets ◽  
Lima Bean ◽  
Amorphous Substance ◽  
Golgi Bodies ◽  
Early Germination ◽  
Almost All ◽  
Vacuolar Content

Changes in cell fine structure were studied in axes of green lima bean seeds soaked in water for 1–48 hours. At the beginning of the imbibition period the cortical and pith cells and to a smaller degree the cells of the future conductive tissues contain several vacuoles filled with an amorphous substance. Almost all of the cells contain lipid droplets arranged exclusively along cell walls. The endoplasmic reticulum appears in the form of long tubules, predominantly occupying the peripheral parts of the cell, surrounding the nucleus. A large concentration of ribosomes, mostly unattached, can be found in the cytoplasm. Similar particles make up the bulk of the nucleolus, but could not be found in plastids, which frequently contained starch, but were devoid of internal membranes. Only very few Golgi bodies occur. No changes in fine structure seem to occur during the first 4 hours of imbibition, but after 24 hours the lipid droplets and the vacuolar content have disappeared, the endoplasmic reticulum is more evenly distributed throughout the cells, and a large number of Golgi bodies can be seen.

scholarly journals FINE STRUCTURE AND ORGANELLE ASSOCIATIONS IN BROWN ALGAE

1965 ◽  
Vol 26 (2) ◽  
pp. 523-537 ◽  
Author(s):  
G. Benjamin Bouck
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Golgi Apparatus ◽  
Nuclear Envelope ◽  
Brown Algae ◽  
Algal Cell ◽  
Plant Cells ◽  
Membrane Systems ◽  
Two Envelopes

The structural interrelationships among several membrane systems in the cells of brown algae have been examined by electron microscopy. In the brown algae the chloroplasts are surrounded by two envelopes, the outer of which in some cases is continuous with the nuclear envelope. The pyrenoid, when present, protrudes from the chloroplast, is also surrounded by the two chloroplast envelopes, and, in addition, is capped by a third dilated envelope or "pyrenoid sac." The regular apposition of the membranes around the pyrenoid contrasts with their looser appearance over the remainder of the chloroplast. The Golgi apparatus is closely associated with the nuclear envelope in all brown algae examined, but in the Fucales this association may extend to portions of the cytoplasmic endoplasmic reticulum as well. Evidence is presented for the derivation of vesicles, characteristic of those found in the formative region of the Golgi apparatus, from portions of the underlying nuclear envelope. The possibility that a structural channeling system for carbohydrate reserves and secretory precursors may be present in brown algae is considered. Other features of the brown algal cell, such as crystal-containing bodies, the variety of darkly staining vacuoles, centrioles, and mitochondria, are examined briefly, and compared with similar structures in other plant cells.

Cytological studies on physodes in the vegetative cells of Cystoseira stricta Sauvageau (Phaeophyta, Fucales)

1980 ◽  
Vol 41 (1) ◽  
pp. 209-231
Author(s):  
L. Pellegrini
Keyword(s):  
Electron Microscopy ◽  
Endoplasmic Reticulum ◽  
Cell Walls ◽  
Higher Plants ◽  
Close Association ◽  
Chloroplast Envelope ◽  
Osmiophilic Granules ◽  
Cytological Changes ◽  
Ultrastructural Characteristics ◽  
Secondary Lysosomes

Physodes have been recognized in meristodermic and promeristematic cells by correlated light- and electron-microscope investigations using different fixation procedures. They are vesicles which contain an osmiophilic material of phenolic nature. Their content changes in appearence according to the fixative used. Osmiophilic deposits are often associated with coiled and disturbed lamellar formations. It has been possible to distinguish several ultrastructural stages which occur during the secretion of the content of the physodes, namely: a chloroplast accumulation and exudation, and a reticular transport to accumulation vacuoles where materials undergo evolution or hydrolysis. Inside plastids, osmiophilic granules are found in close association with thylakoid stacks. They may contain the polyphenolic precursors of physodes, though this has not yet been proved by electron-microscopy procedures. They are expelled from plastids to the chloroplast endoplasmic reticulum. The mechanism of transfer through the chloroplast envelope endoplasmic reticulum. The mechanism of transfer through the chloroplast envelope remains to be elucidated. Lytic activities have been reported inside physodes which might thus act in the same way as the secondary lysosomes of animals and higher plants. Occasionally, the physode content seems to be excreted from the cytoplasm to the cell walls by exocytosis after the probable fusion of plasmalemma and tonoplast. These cytological changes, observed in the vegetative apex of a brown alga, recall some ultrastructural characteristics of the secretory processes described in various glandular tissues of higher plants and which consist of the synthesis, the transport and the elimination of an exudate of flavonic, terpenic or lipophenolic nature.

Changes in Fine Structure of the Potato Meristem Following Heat Treatment for Virus Eradication

1976 ◽  
Vol 24 (5) ◽  
pp. 597 ◽  
Author(s):  
RJ Sward ◽  
ND Hallam
Keyword(s):  
Heat Treatment ◽  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Solanum Tuberosum ◽  
Membrane Systems ◽  
Nutrient Media ◽  
Virus Eradication ◽  
Potato Virus S ◽  
Viral Spread ◽  
Heat Therapy

Potato virus S has been successfully eliminated from the 'Exton' cultivar of the potato (Solanum tuberosum 'Exton'). This has been achieved by a variety of heat treatments and variations in nutrient media for growing meristem tips. As part of this research program we have examined the fine structure of the meristem tips following heat therapy, and aberrant changes were seen in rough endoplasmic reticulum, ribosomes, mitochondria, chloroplasts and membrane systems. A combination of these changes retard viral spread and development within the meristem.

scholarly journals STRUCTURES LINKING THE MYONEMES, ENDOPLASMIC RETICULUM, AND SURFACE MEMBRANES IN THE CONTRACTILE CILIATE VORTICELLA

1973 ◽  
Vol 56 (2) ◽  
pp. 559-579 ◽  
Author(s):  
Richard D. Allen
Keyword(s):  
Endoplasmic Reticulum ◽  
Electron Microscope ◽  
Calcium Ions ◽  
Calcium Release ◽  
Basal Bodies ◽  
Membrane Systems ◽  
Electron Microscope Investigation ◽  
Complex Morphology ◽  
Pass Through ◽  
Er Membrane

An electron microscope investigation of the interface between the myonemes of Vorticella convallaria and their associated endoplasmic reticulum (ER) has revealed structures of a complex morphology linking these two organelles. These structures are named "linkage complexes". Each complex contains a spindle-shaped midpiece which lies in a groove of the ER membrane. Microfilaments splay out from the tips of the midpiece and may come in contact with the inner alveolar sac membrane. Three to six raillike structures lie on each side of the midpiece and parallel it. The ER membrane appears to pass through the sides of the rails. In the lumen of the ER these rails are associated with a meshwork of filaments. A cradle of five rods lies within the groove under the midpiece. The ER membrane also passes through these rods which contact the same meshwork. In the scopular region and in the stalk the microfilaments from the midpiece form a bundle which passes into the lumen of modified basal bodies. These basal bodies are connected to the alveolar sac which, in the stalk, passes as a flattened tube along its length. The parts of the dissociated linkage complex are scattered throughout the spasmoneme of the stalk along membranes of the intraspasmonemal tubules. Thus, both stalk and body contractile bundles have linkage complexes that link their associated membrane systems to the microfibrils and, in turn, connect this membrane-microfibrillar interface to the pellicular membranes. The arrangement of the linkage complex suggests an involvement in the control of the transport of calcium ions between ER and microfibrils, and possibly the transfer of a message from the surface membranes to the sites of calcium release to trigger myonemal contraction.

scholarly journals The Ultrastructure of the Cement Gland in Xenopus laevis

1966 ◽  
Vol 1 (2) ◽  
pp. 193-200 ◽  
Author(s):  
MARGARET M. PERRY ◽  
C. H. WADDINGTON
Keyword(s):  
Endoplasmic Reticulum ◽  
Xenopus Laevis ◽  
Secretory Granules ◽  
Progressive Increase ◽  
Cement Gland ◽  
Membrane Systems ◽  
Large Numbers ◽  
Cytoplasmic Filaments ◽  
Golgi Zone ◽  
Neurula Stage

Alterations which occur during differentiation in the fine structure of the cement gland of the embryo of Xenopus laevis have been investigated. The organ anlage at the late neurula stage is composed of cuboidal cells of comparatively simple cytoplasmic structure. Coincident with the subsequent cellular elongation there is a formation of extensive arrays of functionally interrelated membrane systems, leading to the production of a mucin-like secretory substance. Although there is no direct structural continuity between the membranes of the endoplasmic reticulum and the Golgi apparatus, small vesicles which seem to originate from areas of agranular reticulum appear to transport material synthesized in the endoplasmic reticulum to the Golgi zone. Further elaboration of the product at the site of the Golgi material is suggested by the progressive increase in the quantity of the contents as the cisternae enlarge to form secretory granules. Other notable features of the differentiating cells are microtubules and cytoplasmic filaments, many of which are oriented in the direction of cellular elongation. In suitably preserved specimens, large numbers of glycogen granules are present. The degenerating gland is characterized by the appearance of large autolytic vacuoles within the cytoplasm. Traces of the membrane systems are present and, in many cells, there remain large numbers of secretory granules.

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