The fine structure of the ookinete of Parahaemoproteus velans (= Haemoproteus velans Coatney and Roudabush) (Haemosporidia: Haemoproteidae)

1972 ◽  
Vol 50 (5) ◽  
pp. 477-480 ◽  
Author(s):  
Sherwin S. Desser
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Granular Endoplasmic Reticulum ◽  
Central Nucleus ◽  
Apical Region ◽  
Cylindrical Structures ◽  
Inner Surface

The ookinete of Parahaemoproteus velans is bounded externally by a trilaminar membrane, beneath which lies a fibrillar zone. Below this zone and forming the inner surface of the pellicle is a second, dense, membranelike layer. The specialized apical region of the ookinete is modified into a thickened "caplike" structure. The inner layer of the pellicle in this region is thickened and wavy in appearance. In a sub-pellicular space in the cap region lie about 27 elongate cylindrical structures, and beneath these about 50 microtubules ring the cytoplasm. Numerous dense spherical bodies are located in the anterior cytoplasm of the parasite. A large, more or less central nucleus, often containing microtubular elements, lies in a cytoplasm richly endowed with granular endoplasmic reticulum. Two or more areas containing a "crystalloid" material lie anterior and posterior to the nucleus.

The fine structure of the developing macrogamete of Eimeria maxima

Parasitology ◽  
1979 ◽  
Vol 79 (2) ◽  
pp. 259-265 ◽  
Author(s):  
R. M. Pittilo ◽  
S. J. Ball
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Parasitophorous Vacuole ◽  
The Other ◽  
Granular Endoplasmic Reticulum ◽  
Type I ◽  
Type Ii ◽  
Eimeria Maxima ◽  
Lipid Inclusions

SUMMARYThe fine structure of the developing macrogamete of Eimeria maxima was studied from chicks killed at intervals from 138 to 147 h after inoculation. The macrogamete developed within a parasitophorous vacuole. Lying within this vacuole and extending for some distance around the periphery of the macrogamete were intravacuolar tubules, grouped in certain areas, and in some cases they were seen to make direct connexions with the cytoplasm of the parasite. During development, electron-pale vesicles were pinched off externally from the surface of the macrogamete. There appeared to be 2 forms of wall-forming bodies of the Type I during development, one form being less osmiophilic than the other. Other organelles present, such as wall-forming bodies of Type II, granular endoplasmic reticulum, mitochondria, canaliculi, lipid inclusions and intravacuolar folds, were similar in structure to those of other Eimeria species.

Differentiation of Neurosensory Cells in Hydra

1969 ◽  
Vol 5 (3) ◽  
pp. 699-726
Author(s):  
LOWELL E. DAVIS
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Basal Body ◽  
Neurosecretory Cells ◽  
Nerve Cells ◽  
Granular Endoplasmic Reticulum ◽  
Structural Variations ◽  
Intercellular Bridges ◽  
Undifferentiated Cells

The differentiation of neurosensory cells in Hydra has been studied at the level of the electron microscope. These cells arise from interstitial cells (undifferentiated cells) and not from pre-existing nerve cells. Furthermore, there is no evidence to suggest that neurosensory cells represent a stage in the development of other nerve cells, i.e. ganglionic and neurosecretory cells. Major cytoplasmic changes in fine structure during differentiation include development of a cilium and associated structures (basal body, basal plate, rootlets), development of microtubules and at least two neurites, increase in Golgi lamellae and formation of dense droplets typical of neurosecretory droplets, structural variations in mitochondria and a decrease in the number of ribosomes. Granular endoplasmic reticulum is characteristically poorly developed in all stages of differentiation, including the mature neurosensory cell. Nuclear and nucleolar changes also occur during differentiation but these are less dramatic than the cytoplasmic events. The possibility of neurosensory cells being bi- or multiciliated and the presence of intercellular bridges between these cells are considered. The function of neurosensory cells is discussed briefly in relation to the function of the cilium and neurosecretory droplets.

The fine structure of Leucocytozoon simondi. V. The oocyst

1972 ◽  
Vol 50 (6) ◽  
pp. 707-711 ◽  
Author(s):  
Sherwin S. Desser
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Basal Lamina ◽  
Central Core ◽  
Granular Endoplasmic Reticulum ◽  
Midgut Epithelium ◽  
Stage Of Development ◽  
Peripheral Cytoplasm

Following penetration through the midgut epithelium of Simulium rugglesi, ookinetes of Leucocytezoon simondi round up beneath the basal lamina and transform into young oocysts. These spherical, walled structures contain a large central core of crystalloid material. Dividing nuclei are seen in the peripheral cytoplasm, which is characterized by several concentric layers of granular endoplasmic reticulum. In a succeeding stage of development the trilaminar plasma membrane appears intermittently doubled, and bud-like outgrowths occur in these thickened areas. At this stage the crystalloid material is dispersed throughout the cytoplasm. A nucleus, an elongate mitochondrion, and some crystalloid material move into each forming sporozoite, which continues to grow at the expense of the residual cytoplasm.

Insect frontal ganglion: fine structure of its neurosecretory cells in diapause and non-diapause larvae of Diatraea grandiosella

1975 ◽  
Vol 53 (8) ◽  
pp. 1093-1100 ◽  
Author(s):  
C.-M. Yin ◽  
G. M. Chippendale
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Neurosecretory Cells ◽  
Granular Endoplasmic Reticulum ◽  
Diatraea Grandiosella ◽  
Corn Borer ◽  
Golgi Bodies ◽  
Juvenile Hormone Mimic ◽  
Frontal Ganglion ◽  
Southwestern Corn Borer

The fine structure of the neurosecretory (NS) cells of the frontal ganglion (FG) of diapause and non-diapause mature larvae of the southwestern corn borer, Diatraea grandiosella, was compared. Two large (15- to 20-μm diam) NS cells are typically found in each FG. Their cytoplasm stained deeply purple with paraldehyde fuchsin and contained granules 1500–2500 Å in diameter. The granules in the NS cells of non-diapause larvae were often associated with Golgi bodies whereas those of the diapause larvae were associated with dilated cisternae of the granular endoplasmic reticulum. Fewer Golgi bodies were observed in sections of NS cells of the FG of diapause larvae than in those of non-diapause larvae. Sections prepared from diapause larvae obtained conventionally by exposure to low temperatures, and experimentally by treatment with a juvenile hormone mimic, gave similar results.Our findings show that granules accumulate in the perikaryon of the NS cells of the FG of diapause larvae and suggest that the granular endoplasmic reticulum is involved in their formation. The shutdown of the transport of these NS granules from the FG appears to be a factor in some yet to be determined phase of the neuroendocrine regulation of diapause.

The structure and development of the macrogamete and oocyst of Eimeria acervulina

Parasitology ◽  
1971 ◽  
Vol 62 (1) ◽  
pp. 31-34 ◽  
Author(s):  
D. L. Lee ◽  
B. J. Millard
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Technical Assistance ◽  
Granular Endoplasmic Reticulum ◽  
Type Ii ◽  
Oocyst Wall ◽  
Eimeria Acervulina ◽  
Early Stages

The fine structure of the macrogametocyte, macrogamete and the early stages in the formation of the oocyst wall of Eimeria acervulina have been described and compared with other species of Eimeria. It has been shown that type II wall-forming bodies are formed in cisternae of the granular endoplasmic reticulum in association with Golgi complexes. The developing oocyst has been shown to be enclosed by three membranes: the outermost is the original membrane of the merozoite and macrogametocyte; the second membrane appears when the wall-forming bodies are appearing in the cytoplasm of the macrogametocyte and the innermost membrane appears after fertilization. The wall-forming bodies discharge their contents between the innermost membrane and the middle membrane.We wish to thank Mr P. L. Long for much valuable discussion, Mrs B. Fisher for technical assistance and Mr B. Carter for assistance with the photography.

The fine structure of Leucocytozoon simondi. III. The ookinete and mature sporozoite

1970 ◽  
Vol 48 (4) ◽  
pp. 641-645 ◽  
Author(s):  
Sherwin S. Desser
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Transverse Section ◽  
Crystalline Material ◽  
Apical Region ◽  
Nuclear Region ◽  
Food Material ◽  
Polar Ring ◽  
Inner Surface

The pellicles of ookinetes and sporozoites of Leucocytozoon simondi measure about 40 mμ and are similar in appearance. The parasites are bounded externally by a trilaminar plasma membrane beneath which lies a fibrillar zone. Below this zone and forming the inner surface of the pellicle is a second membrane-like layer. The specialized apical region of the ookinete is modified into a thickened "cap-like" structure. The pellicle in this apical cap region appears wavy and the inner layer appears allernately thick and thin in transverse section. In the subpellicular space lie numerous long thickened structures suggestive of struts which line the inner surface of the apical cap. Beneath these, about 70 microtubules ring the cytoplasm. Numerous dense elongate micronemes extend anteriorly toward the apex of the ookinete. The anterior tip of the pellicle of sporozoites is modified into a cup-like conoid and a polar ring with which about 35 subpellicular microtubules are associated. Elongate paired organelles extend anteriorly from the nuclear region to the polar ring. Numerous dense, ellipsoidal granules and one or more mitochondria are seen in the cytoplasm. A crystalline material which corresponds with the "vacuoles" observed in Giemsa-stained ookinetes and sporozoites lies in two or more zones within the cytoplasm and may be a stored food material or possibly a virus.

Fine structure of the apical rim—mesenchyme complex during limb morphogenesis in man

Development ◽  
1973 ◽  
Vol 29 (1) ◽  
pp. 117-131
Author(s):  
Robert O. Kelley
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Basal Lamina ◽  
Granular Endoplasmic Reticulum ◽  
Limb Morphogenesis ◽  
Junctional Complexes

Ultrastructure of the apical rim–basal lamina–mesenchyme complex in man during Horizons 15–18 is correlated with the development of limbs. 1. Apical epithelium is a complicated tissue exhibiting surface microvilli, junctional complexes, free ribosomes, elaborate Golgi centers, glycogen and scanty granular endoplasmic reticulum. 2. The apical rim thickens during stages 15 and 16, remaining multilayered at digital tips and thinning adjacent to zones of necrosis by stages 17 and 18. Epithelial thinning may be a response to lack of ‘maintenance factor’. 3. A continuous basal lamina is present during these stages. Collagen-like fibrils are numerous in interdigital zones of necrosis and sparse at tips of digital blastemata. 4. The presence of oriented microfilaments in interdigital epithelium suggests active invagination during morphogenesis of fingers in man.

scholarly journals THE FINE STRUCTURE OF BONE CELLS

1961 ◽  
Vol 11 (3) ◽  
pp. 627-649 ◽  
Author(s):  
H. Robert Dudley ◽  
David Spiro
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Bone Cells ◽  
Amorphous Material ◽  
Granular Endoplasmic Reticulum ◽  
Lamellar Bone ◽  
Cell Surfaces ◽  
Progressive Reduction ◽  
Electron Microscopic ◽  
Cytoplasmic Processes

An electron microscopic study of Araldite-embedded, undecalcified human woven and chick lamellar bone is presented. The fine structure of the cells of bone in their normal milieu is described. Active osteoblasts possess abundant granular endoplasmic reticulum, numerous small vesicles, and a few secretion droplets. Their long cytoplasmic processes penetrate the osteoid. The transition of osteoblasts into osteoid osteocytes and then into osteocytes is traced and found to involve a progressive reduction of cytoplasmic organelles. Adjoining the osteocytes and their processes is a layer of amorphous material which is interposed between the cell surfaces and the bone walls of their respective cavities. Osteoclasts contain numerous non-membrane-associated ribosomes, abundant mitochondria, and little granular endoplasmic reticulum, thus differing markedly from other bone cells. The brush border is a complex of cytoplasmic processes adjacent to a resorption zone in bone. No unmineralized collagen is seen at resorption sites and it appears that collagen is removed before or at the time of mineral solution. All bone surfaces are covered by cells, some of which lack distinctive qualities and are designated endosteal lining cells. The structure of osteoid, bone, and early mineralization sites is illustrated and discussed.

scholarly journals THE EFFECTS OF ENUCLEATION ON THE CYTOPLASMIC MEMBRANES OF AMOEBA PROTEUS

1968 ◽  
Vol 37 (2) ◽  
pp. 300-315 ◽  
Author(s):  
Charles J. Flickinger
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Electron Microscope ◽  
Golgi Apparatus ◽  
Amoeba Proteus ◽  
Granular Endoplasmic Reticulum ◽  
Whole Cells ◽  
Golgi Bodies ◽  
Cytoplasmic Membranes ◽  
In Cells

The dependence of cytoplasmic membranes upon the nucleus was studied by examining enucleated amebae with the electron microscope at intervals up to 1 wk after enucleation. Amebae were cut into two approximately equal parts, and the fine structure of the enucleated portions was compared with that of the nucleated parts and starved whole cells which had been maintained under the same conditions. Golgi bodies were diminished in size 1 day after enucleation and were not detected in cells enucleated for more than 2 days. The endoplasmic reticulum of enucleated cells appeared to increase in amount and underwent changes in its morphology. The sparsely scattered short tubules of granular endoplasmic reticulum present in unmanipulated amebae from stock cultures were replaced in 1–3-day enucleates by long narrow cisternae. In 3–7-day enucleates, similar cisternae of granular endoplasmic reticulum encircled areas of cytoplasm partially or completely. It was estimated that in most cases hundreds of these areas encircled by two rough membranes were formed per enucleated cell. The number of ribosomes studding the surface of the endoplasmic reticulum decreased progressively with time after enucleation. In contrast, the membranes of nucleated parts and starved whole cells did not undergo these changes. The possible identification of membrane-encircled areas as cytolysomes and their mode of formation are considered. Implications of the observations regarding nuclear regulation of the form of the Golgi apparatus and the endoplasmic reticulum are discussed.

Ultrastructure and development of urediospore ornamentation in Melampsora lini

1971 ◽  
Vol 49 (12) ◽  
pp. 2067-2073 ◽  
Author(s):  
L. J. Littlefield ◽  
C. E. Bracker
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Outer Surface ◽  
Spore Wall ◽  
Wall Material ◽  
Wild Type ◽  
Melampsora Lini ◽  
Inner Surface ◽  
External Position ◽  
Basal Portion

The urediospores of Melampsora lini (Ehrenb.) Lev. are echinulate, with spines ca. 1 μ long over their surface. The spines are electron-transparent, conical projections, with their basal portion embedded in the electron-dense spore wall. The entire spore, including the spines, is covered by a wrinkled pellicle ca. 150–200 Å thick. The spore wall consists of three recognizable layers in addition to the pellicle. Spines form initially as small deposits at the inner surface of the spore wall adjacent to the plasma membrane. Endoplasmic reticulum occurs close to the plasma membrane in localized areas near the base of spines. During development, the spore wall thickens, and the spines increase in size. Centripetal growth of the wall encases the spines in the wall material. The spines progressively assume a more external position in the spore wall and finally reside at the outer surface of the wall. A mutant strain with finely verrucose spores was compared to the wild type. The warts on the surface of the mutant spores are rounded, electron-dense structures ca. 0.2–0.4 μ high, in contrast to spines of the wild type. Their initiation near the inner surface of the spore wall and their eventual placement on the outer surface of the spore are similar to that of spines. The wall is thinner in mutant spores than in wild-type spores.

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