The Fine Structure of Chloroplasts and Pyrenoids in Some Marine Dinoflagellates

1968 ◽  
Vol 3 (1) ◽  
pp. 41-47
Author(s):  
J. D. DODGE
Keyword(s):  
Fine Structure ◽  
Granular Material ◽  
Lipid Droplets ◽  
Marine Dinoflagellates ◽  
Chloroplast Stroma ◽  
Transparent Area ◽  
Electron Transparent Area

The chloroplasts of some members of the Dinophyceae are bounded by an envelope consisting of three membranes and having a mean thickness of 230 A°. Within the chloroplast are arranged, in a more or less parallel manner, many lamellae normally composed of three apposed thylakoids, although the number of thylakoids often varies and may reach 30 in a single stack. By study of disintegrated chloroplasts it was found that the thylakoids are circular in shape with a diameter of 0.15-3.6 µ and a mean thickness of 240 A°;. Ribosomes, lipid droplets and DNA areas are present in the chloroplast stroma. No connexions were seen between the chloroplasts and any other organelles, nor did the chloroplasts contain girdle lamellae. Stalked pyrenoids, which are found in some dinoflagellates, are shown to arise from the inner face of the chloroplasts, to contain a finely granular material and to be frequently surrounded by an electron-transparent area. These findings are discussed in relation to the fine structure of the chloroplasts and pyrenoids of other algal classes.

Fine structure of basidiospores of the cedar-apple rust fungus Gymnosporangium juniperi-virginianae

1977 ◽  
Vol 55 (9) ◽  
pp. 1057-1063 ◽  
Author(s):  
Charles W. Mims
Keyword(s):  
Fine Structure ◽  
Thin Layer ◽  
Lipid Droplets ◽  
Germ Tube ◽  
Rust Fungus ◽  
Spore Wall ◽  
Lipid Bodies ◽  
Pore Region ◽  
Hilar Region ◽  
Endoplasmic Reticula

Each basidiospore of Gymnosporangium juniperi-virginianae contains many ribosomes as well as lipid droplets, mitochondria, small vesicles, endoplasmic reticula, and structures thought to be microbodies. Mature spores are either uninucleate or binucleate although larger, tetranucleate spores were occasionally observed. The spore wall appears as a thin layer except around the hilar region where two layers are evident. Germination is almost always lateral although no germ pore region was noted in the wall. Vacuolation takes place during germination and lipid bodies disappear. The wall of the germ tube arising from the spore is continuous with that of the spore. A large number of vesicles is present in the germ tube. Basidiospores may also germinate by repetition.

scholarly journals THE AXON HILLOCK AND THE INITIAL SEGMENT

1968 ◽  
Vol 38 (1) ◽  
pp. 193-201 ◽  
Author(s):  
Sanford L. Palay ◽  
Constantino Sotelo ◽  
Alan Peters ◽  
Paula M. Orkand
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Granular Material ◽  
Internal Structure ◽  
Electron Micrographs ◽  
Initial Segment ◽  
Special Function ◽  
Structural Features ◽  
Dense Layer ◽  
Axon Hillock

Axon hillocks and initial segments have been recognized and studied in electron micrographs of a wide variety of neurons. In all multipolar neurons the fine structure of the initial segment has the same pattern, whether or not the axon is ensheathed in myelin. The internal structure of the initial segment is characterized by three special features: (a) a dense layer of finely granular material undercoating the plasma membrane, (b) scattered clusters of ribosomes, and (c) fascicles of microtubules. A similar undercoating occurs beneath the plasma membrane of myelinated axons at nodes of Ranvier. The ribosomes are not organized into Nissl bodies and are too sparsely distributed to produce basophilia. They vanish at the end of the initial segment. Fascicles of microtubules occur only in the axon hillock and initial segment and nowhere else in the neuron. Therefore, they are the principal identifying mark. Some speculations are presented on the relation between these special structural features and the special function of the initial segment.

The fine structure of chloroplast stroma crystals

1973 ◽  
Vol 45 (1-2) ◽  
pp. 50-58 ◽  
Author(s):  
Christer Larsson ◽  
Curt Collin ◽  
Per-Åke Albertsson
Keyword(s):  
Fine Structure ◽  
Chloroplast Stroma

Ultrastructural Studies on the Effects of Korean Panax Ginseng on the Theca Interna of Rat Ovary

1979 ◽  
Vol 07 (04) ◽  
pp. 333-344 ◽  
Author(s):  
Moo Rim Byung
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Golgi Apparatus ◽  
Panax Ginseng ◽  
Lipid Droplets ◽  
Ultrastructural Studies ◽  
Dense Bodies ◽  
Rat Ovary ◽  
Theca Interna ◽  
Morphologic Changes

An investigation was conducted to delineate the fine structure of steroid-producing ovarian theca interna cells following administration of Korean Panax ginseng to rats for 60 days. The cytoplasmic changes were observed in the ginseng-treated theca interna cells, increased number, size and density of the mitochondria, and increased size of the smooth surfaced endoplasmic reticulum, the rough surfaced endoplasmic reticulum and the Golgi apparatus. The nucleus and nucleolus were slightly enlarged and increased numbers of dense bodies were seen whereas lipid droplets were decreased in number. The changes may result from hyperfunction of the steroid-producing cells. Morphologic changes seen may represent stimulating effects on the steroid-producing cells of the theca interna in ginseng-treated animals.

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 Inversion of force lines in fiber-reinforced jammed granular material

2021 ◽  
Vol 44 (4) ◽  
Author(s):  
Pavel S. Iliev ◽  
Falk K. Wittel ◽  
Hans J. Herrmann
Keyword(s):  
Fine Structure ◽  
Granular Material ◽  
Fiber Reinforced ◽  
Dynamic Simulations ◽  
Contact Networks ◽  
Particle Contact ◽  
Rigid Particles

Abstract Freestanding columns, built out of nothing but loose gravel and continuous strings can be stable even at several meters in height and withstand vertical loads high enough to severely fragment grains of the column core. We explain this counter-intuitive behavior through dynamic simulations with polyhedral rigid particles and elastic wire chains. We evaluate the fine structure of the particle contact networks, as well as confining forces and reveal fundamental intrinsic differences to the well-studied case of confining silos. Graphic abstract

Misfit dislocations in heteroepitaxial systems with low dislocation density

1978 ◽  
Vol 36 (1) ◽  
pp. 132-133
Author(s):  
W. Hagen ◽  
H. Strunk
Keyword(s):  
Electron Microscopy ◽  
Dislocation Density ◽  
Misfit Dislocations ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Transmission Electron ◽  
Low Dislocation Density ◽  
Heteroepitaxial Layers ◽  
Transparent Area ◽  
Electron Transparent Area

The growth of heteroepitaxial layers causes stress across the interface which in a certain range of layer thickness may he relaxed by the formation of misfit dislocations at the interface. Systematic investigations of such misfit structures by transmission electron microscopy (TEM) have previously heen conducted only on systems with a relatively large misfit parameter f, i.e. with a high dislocation density. However, this case presents difficulties in the analysis because of the complexity of the dense structures.Interfaces containing a low density of misfit dislocations, e.g. heteroepitaxial systems with low misfit, should consequently be investigated. High voltage electron microscopy (HVEM) enables us to study specimens of several μm in thickness and offers decisive advantages over 100 kV TEM: i) generally, specimens can he prepared by thinning the substrate only, ii) thick foils are mechanically stable, which allows the preparation of specimens with an electron transparent area of several mm2.We report here new results on the initial formation of misfit dislocation structures in the heteroepitaxial system Ge on GaAs (f = 0.074%).

HREM applications to industrial products: Observation of thick-film resistors with very large electron transparent area

1992 ◽  
Vol 50 (1) ◽  
pp. 140-141
Author(s):  
Z.G. Li ◽  
P.F. Carcia ◽  
P. Donohue
Keyword(s):  
Thick Film ◽  
Semiconductor Industry ◽  
Milling Process ◽  
Ion Milling ◽  
Secondary Support ◽  
Characterization Of Materials ◽  
Transparent Area ◽  
Electron Transparent Area ◽  
Section Sample

HRTEM is a very powerful tool for structural characterization of materials. However, its role in industry is still very limited and electron microscopy is generally considered as a secondary support technique, although it can uniquely provide microstructural information leading to understanding and improvement of product quality, especially for those materials in the form of films. An example in the semiconductor industry is recendy described by Anderson. He points out that the main concerns of imaging using a conventional cross-section sample preparation method are too small imaged areas, not representative of the product, and artifacts that may be introduced during the ion-milling process. Here we apply HREM to thick film resistors and attempt to overcome these obstacles.

The fine structure and ontogeny of trichocysts in marine dinoflagellates

PROTOPLASMA ◽  
1966 ◽  
Vol 61 (1-2) ◽  
pp. 205-223 ◽  
Author(s):  
G. Benjamin Bouck ◽  
Beatrice M. Sweeney
Keyword(s):  
Fine Structure ◽  
Marine Dinoflagellates

Fine structure of Tyloses in three species of the Myrtaceae

1967 ◽  
Vol 15 (1) ◽  
pp. 25 ◽  
Author(s):  
RC Foster
Keyword(s):  
Fine Structure ◽  
Granular Material ◽  
Double Layer ◽  
Layered Structure ◽  
Outer Layer ◽  
Secondary Wall ◽  
Pit Membrane ◽  
Ray Cell

The tylosis wall in Eucalyptus obliqua L'Herit. is shown to be composed of two microfibrillar layers. The outer layer (T1), with randomly orientated microfibrils, is covered with amorphous granular material. The inner layer (T2) is multilamellate. In sclerosed tyloses of E. miniata A. Cunn., each lamella of T2 is composed of many layers of microfibrils. Simple pits, delineated by circumferentially orientated microfibrils, are found in both sclerosed and non-sclerosed tyloses. The tylosis in E. obliqua is shown to arise from a two-layered structure formed within the secondary wall of the ray cell. This layer extends into the pit chamber, covering the pit membrane on the ray side. Following the breakdown of the vestures and the pit membrane, this double layer bulges out into the vessel to form the tylosis.

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