The apical structure in Perophora annectens (tunicate) spermatozoa: fine structure, differentiation and possible role in fertilization

1984 ◽  
Vol 66 (1) ◽  
pp. 175-187
Author(s):  
M. Fukumoto
Keyword(s):  
Fine Structure ◽  
Golgi Apparatus ◽  
Dense Material ◽  
Electron Dense Material ◽  
Extracellular Materials ◽  
Small Blister

The apical structure in Perophora annectens spermatozoa is approximately 4 micron in length and it is helically coiled. Its major component is a striated structure, which may be analogous to a perforatorium. The plasmalemma enclosing the anterior quarter of the apical structure is covered by extracellular materials, the anterior ornaments. During spermiogenesis, the apical structure is first recognized as a small blister of the plasmalemma at the apex of the young spermatid. It develops into a conical protrusion and then into a finger-like process (approximately 1 micron in length). This process is transformed into an elongated process (approximately 4 micron in length) with electron-dense material in its core. Finally, the elongated process is helically coiled to form an apical structure in which electron-dense material forms dense striations. Vesicles (50-70 nm in diameter), presumably derived from the Golgi apparatus, have been recognized in the blisters of younger spermatids, and can be followed through to the finger-like process. In the finger-like process these vesicles are transformed into smaller vesicles (20-30 nm in diameter), which probably fuse with the anterior plasmalemma of the finger-like process. This suggests that chorion lysin(s) is associated with the anterior membrane enclosing the apical structure in these spermatozoa.

Osmoregulation in the alga Vacuolaria virescens. Structure of the contractile vacuole and the nature of its association with the Golgi apparatus

1978 ◽  
Vol 31 (1) ◽  
pp. 213-224
Author(s):  
P. Heywood
Keyword(s):  
Golgi Apparatus ◽  
Contractile Vacuole ◽  
Dense Material ◽  
Anterior Surface ◽  
Electron Dense Material ◽  
Golgi Vesicles ◽  
Hexagonal Pattern ◽  
Permanent Structure ◽  
Lateral Walls

The contractile vacuole of the chloromonadophycean alga Vacuolaria virescens is a permanent structure that possesses a specialized membrane: subunits of this membrane have a diameter of 21–24 nm and in places are arranged in a regular hexagonal pattern. The lateral walls of these subunits form regularly spaced bristles or pegs which extend inwards from the trilaminar membrane for a distance of 13–15 nm. The contractile vacuole is situated immediately above an extensive Golgi apparatus that covers most of the anterior surface of the nucleus. Vesicles of Golgi origin give rise to subsidiary vacuoles which in turn empty into the contractile vacuole. Golgi vesicles, subsidiary vacuoles and the contractile vacuole contain similar electron-dense material. It is suggested that this material might be a highly hydrophilic substance which will attract water from the cytoplasm into the Golgi vesicles, subsidiary vacuoles and contractile vacuole from whence it is discharged from the cell. This method of osmoregulation is compared to that occurring in other algae and protozoa.

Fine structure of surface and sunken grooved pegs on the antenna of female Anopheles stephensi (Diptera: Culicidae)

1976 ◽  
Vol 54 (2) ◽  
pp. 235-244 ◽  
Author(s):  
K. S. Boo ◽  
S. B. McIver
Keyword(s):  
Fine Structure ◽  
Electron Density ◽  
Anopheles Stephensi ◽  
Olfactory Receptors ◽  
The Other ◽  
Dense Material ◽  
Extracellular Material ◽  
Electron Dense Material ◽  
Subtype B ◽  
Antenna Surface

The antenna of female Anopheles stephensi Liston bears three types of sensilla with grooved pegs: those sunken in pits and subtypes A and B of those located on the flagellar surface. The sunken peg sensilla are innervated by four or five neurons with branching dendrites. The dendrites are exposed to the exterior by means of longitudinal clefts at the bases of the grooves in the peg wall. Surrounding the dendrites and extending into the clefts is an extracellular material of medium electron density. Three sheath cells are associated with each sunken peg sensillum.Subtype-A surface peg sensilla are generally similar to the sunken peg sensilla, except that they are located on the antenna) surface and are innervated by two neurons with unbranched dendrites. Subtype-B surface peg sensilla have three or four neurons, the dendrites of which do not branch and are exposed less to the exterior than those in the other peg sensilla because the clefts in the peg wall are smaller and less frequent. Only trace amounts of electron-dense material occur in the clefts of the subtype-B surface peg sensilla.The sunken peg and both subtypes of the surface peg sensilla are probably olfactory receptors.

The ultrastructure of the R.S. zoospore of the Chytridiomycete Physoderma gerhardti

1978 ◽  
Vol 56 (12) ◽  
pp. 1387-1393 ◽  
Author(s):  
Robert J. Lowry ◽  
Frederick K. Sparrow
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Inclusion Bodies ◽  
Smooth Endoplasmic Reticulum ◽  
Lipid Body ◽  
Dense Material ◽  
Electron Dense Material ◽  
General Internal ◽  
Deep Groove ◽  
Posterior Flagellum

The fine structure of the zoospore of Physoderma gerhardti Schroeter is described. It possesses a single very large lipid body (sometimes accompanied by several smaller ones) situated laterally to the nuclear cap – nucleus complex and is associated with electron-dense material (the microbody) and the single large posteriorly located mitochondrion. The single posterior flagellum proximally terminates in a kinetosome just short of the posterior cone-shaped end of the nucleus. The kinetosome lies in a deep groove in the mitochondrion and is associated with this organelle by striated rootlets. The kinetosome terminates in electron-dense material from which an array of microtubules arises. These microtubules run along the sides of the cone-shaped nucleus and nuclear cap. There is an accessory centriole lying close to and more or less parallel with the kinetosome. The cytoplasm contains a small amount of smooth endoplasmic reticulum and several inclusion bodies in the anterior region and several small vacuoles in the posterior region of the cell. The general internal organization of the zoospore of Physoderma gerhardti more nearly resembles that of a blastocladiaceous fungus than of any chytrid thus far investigated.

The Fine Structure Produced in Cells by Primary Fixatives

1963 ◽  
Vol s3-104 (65) ◽  
pp. 101-106
Author(s):  
JOHN R. BAKER ◽  
BARBARA M. LUKE
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Golgi Apparatus ◽  
Mercuric Chloride ◽  
Chloride Solution ◽  
Zymogen Granules ◽  
Electron Dense Material ◽  
Mouse Pancreas ◽  
Exocrine Cells ◽  
Mercuric Chloride Solution

The exocrine cells of the mouse pancreas were fixed in mercuric chloride solution, embedded in plexigum, and examined by electron microscopy. The cytoplasm was found to be coagulated as a continuous substance containing innumerable subspherical cavities, mostly between 40 and 200 mµ in diameter and separate from one another. The zymogen granules were preserved, but no trace remained of mitochondria or Golgi apparatus. The nuclear sap was coagulated as a coarse network with thickenings at the nodes. Lumps of electron-dense material (? DNA) were present at the periphery of the nucleus and round the nucleolus. The proteins of the cell appear to have been fixed by mercuric chloride, but the membranous constituents, which rely for their form on a phospholipid component, are not clearly recognizable. The lipids have presumably been lost during dehydration and embedding.

Comparative Morphology of Intercellular Bridges Between Developing Germ Cells of the Ovary

1970 ◽  
Vol 28 ◽  
pp. 328-329
Author(s):  
J. R. Ruby ◽  
R. F. Dyer ◽  
R. G. Skalko ◽  
R. F. Gasser ◽  
E. P. Volpe
Keyword(s):  
Germ Cells ◽  
Rana Pipiens ◽  
Comparative Morphology ◽  
Dense Material ◽  
Individual Species ◽  
Microscope Examination ◽  
Electron Dense Material ◽  
Intercellular Bridges ◽  
Cytoplasmic Side ◽  
Intercellular Connections

An electron microscope examination of fetal ovaries has revealed that developing germ cells are connected by intercellular bridges. In this investigation several species have been studied including human, mouse, chicken, and tadpole (Rana pipiens). These studies demonstrate that intercellular connections are similar in morphology regardless of the species.Basically, all bridges are characterized by a band of electron-dense material on the cytoplasmic side of the tri-laminar membrane surrounding the connection (Fig.l). This membrane is continuous with the plasma membrane of the conjoined cells. The dense material, however, never extends beyond the limits of the bridge. Variations in the configuration of intercellular connections were noted in all ovaries studied. However, the bridges in each individual species usually exhibits one structural characteristic seldom found in the others. For example, bridges in the human ovary very often have large blebs projecting from the lateral borders whereas the sides of the connections in the mouse gonad merely demonstrate a slight convexity.

The ultrastructure of M1-a-mediated resistance to powdery mildew infection in barley

1975 ◽  
Vol 53 (22) ◽  
pp. 2589-2597 ◽  
Author(s):  
H. H. Edwards
Keyword(s):  
Powdery Mildew ◽  
Host Cell ◽  
Electron Density ◽  
Epidermal Cells ◽  
Dense Material ◽  
Ultrastructural Changes ◽  
Electron Dense Material ◽  
Host Cytoplasm ◽  
Powdery Mildew Infection ◽  
Cell Protoplast

M1-a-mediated resistance in barley to invasion by the CR3 race of Erysiphe graminis f. sp. hordei does not occur in every host cell with the same speed and severity. In some cells ultrastructural changes within the host cell as a result of resistance will occur within 24 h after inoculation, whereas in other cells these changes may take up to 72 h. In some cells the ultrastructural changes are so drastic that they give the appearance of a hypersensitive death of the host cell, whereas in other cells the changes are very slight. In any case, at the end of these changes the fungus ceases growth. The ultrastructural changes occur in penetrated host epidermal cells as well as non-infected adjacent epidermal and mesophyll cells.The following ultrastructural changes have been observed: (1) an electron-dense material which occurs either free in the vacuole or adhering to the tonoplast (the material is granular or in large clumps); (2) an increased electron density of the host cytoplasm and nucleus; (3) a breakdown of the tonoplast so that the cytoplasmic constituents become dispersed throughout the cell lumen; and (4) the deposition of papillar-like material in areas other than the penetration site. The first three changes take place within the host cell protoplasts and are directly attributable to the gene M1-a. These changes are typical of stress or incompatibility responses and thus M1-a appears to trigger a generalized incompatibility response in the presence of race CR3. The papillar-like material occurs outside the host cell protoplast in the same manner as the papilla and probably is not directly attributable to M1-a.

Fine structure and development of schizonts, merozoites and macrogamonts of Eimeria acervulina in the goblet cells of the duodenal epithelium of experimentally infected birds

Parasitology ◽  
1975 ◽  
Vol 70 (2) ◽  
pp. 223-229 ◽  
Author(s):  
E. Michael
Keyword(s):  
Fine Structure ◽  
Epithelial Cells ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Goblet Cells ◽  
Cellular Level ◽  
Site Specificity ◽  
Eimeria Acervulina ◽  
Duodenal Epithelium

The fine structure of trophozoites, schizonts, merozoites and macrogamonts of Eimeria acervulina found in goblet cells of the duodenal epithelium of chicks is described and compared with the corresponding stages formed in other epithelial cells. Complete schizogony, with the formation of mature merozoites, occurred freely in goblet cells. Developing macrogamonts (but no microgamonts) were rarely found in goblet cells. The stages observed were confined to the cytoplasm of the host cell above the Golgi apparatus and were usually seen between the mucous granules. The stages seen appeared normal, and contained similar structures to corresponding stages developing in other cells. The finding of developing stages of E. acervulina in goblet cells provides further evidence that site specificity of Eimeria at the cellular level is not as strict as previously thought.

scholarly journals Growth and Differentiation of the Golgi Apparatus in the Red Alga, Callithamnion Roseum

1974 ◽  
Vol 14 (3) ◽  
pp. 633-655
Author(s):  
EVA KONRAD HAWKINS
Keyword(s):  
Plasma Membrane ◽  
Fine Structure ◽  
Golgi Apparatus ◽  
Red Algae ◽  
Developmental Stages ◽  
Spore Wall ◽  
Red Alga ◽  
Wall Formation ◽  
Golgi Vesicles

The fine structure of the Golgi apparatus during development of tetrasporangia of Calli-thamnion roseum is described. Dictyosomes and associated vesicles of 4 developmental stages of sporangia are examined. The wall of sporangia exhibits a heretofore unseen cuticle in red algae. Development of the spore wall and a new plasma membrane around spores occurs through fusion of adjacent Golgi vesicles along the periphery of cells. Observations are discussed in relation to wall formation and expansion of tetrads and in comparison with other work on growth and differentiation of the Golgi apparatus.

scholarly journals The fine structure produced in cells by primary fixatives 2. Potassium dichromate

1965 ◽  
Vol s3-106 (73) ◽  
pp. 15-21
Author(s):  
JOHN R. BAKER
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Fine Structure ◽  
Golgi Apparatus ◽  
Nuclear Membrane ◽  
Osmium Tetroxide ◽  
Potassium Dichromate ◽  
Potassium Dichromate Solution ◽  
Zymogen Granules ◽  
Mouse Pancreas

The exocrine cells of the mouse pancreas were fixed in potassium dichromate solution, embedded in araldite or other suitable medium, and examined by electron microscopy. Almost every part of these cells is seriously distorted or destroyed by this fixative. The ergastoplasm is generally unrecognizable, the mitochondria and zymogen granules are seldom visible, and no sign of the plasma membrane, microvilli, or Golgi apparatus is seen. The contents of the nucleus are profoundly rearranged. It is seen to contain a large, dark, irregularly shaped, finely granular object; the evidence suggests that this consists of coagulated histone. The sole constituent of the cell that is well fixed is the inner nuclear membrane. The destructive properties of potassium dichromate are much mitigated when it is mixed in suitable proportions with osmium tetroxide or formaldehyde.

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