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.

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.

Ultrastructure of mitosis in the chloromonadophycean alga Vacuolaria virescens

1978 ◽  
Vol 31 (1) ◽  
pp. 37-51
Author(s):  
P. Heywood
Keyword(s):  
Golgi Apparatus ◽  
Nuclear Envelope ◽  
Genetic Material ◽  
Membrane Vesicles ◽  
Contractile Vacuole ◽  
Basal Bodies ◽  
Anterior Surface ◽  
Daughter Cells ◽  
Interphase Cells ◽  
Unusual Type

During preprophase in the chloromonadophycean alga Vacuolaria virescens microtubules are present around the flagellar basal bodies and extend over the anterior surface of the nucleus. These microtubules assist in the separation of the flagella and later enter the nucleus through polar gaps. During prophase the nucleoli begin to disperse and the chromosomes become condensed. At metaphase the nucleus assumes an elliptical shape and an equatorial plate of chromosomes becomes aligned across the long axis of the nucleus; kinetochores are recognizable on some of the chromosomes. The nuclear envelope remains intact over most of the surface and in places it forms folds. During anaphase chromosomes are less distinct and vesicles are present in the elongating nucleus. Most of the new nuclear envelope around the progeny nuclei is formed by coalescence of these membrane vesicles during late anaphase and telophase, although some of the original nuclear envelope may also become incorporated. During telophase disintegration of the original nuclear envelope becomes pronounced and portions of this structure are recognizable in the cytoplasm after completion of mitosis. It is suggested that this unusual type of nuclear envelope behaviour may be important in ensuring the segregation of the Golgi apparatus and contractile vacuole to progeny cells. Interphase cells contain a single extensive Golgi apparatus which is located between the anterior surface of the nucleus and the contractile vacuole. The Golgi apparatus and contractile vacuole act as an osmoregulatory system and their presence is presumably essential to the existence of the organism. Formation of a new contractile vacuole and division of the Golgi apparatus occur early in mitosis and thereafter a Golgi apparatus and contractile vacuole become associated with each of the poles of the nucleus. They retain this location throughout mitosis and during cytokinesis, with the result that an osmoregulatory system is present in each of the daughter cells. In a similar manner, microbody-like organelles are associated with the nuclear envelope during mitosis but not at interphase. Growth of the nuclear envelope during mitosis may serve as the means of partitioning these organelles to the progeny cells. Thus mitosis in Vacuolaria virescens is responsible not only for the equal segregation of the genetic material but also for the correct distribution of some of the cytoplasmic components.

Golgi Apparatus and Melanogenesis: Ultrastructural Study of a Human Cellular Blue Nevus (Melanocytoma)

1973 ◽  
Vol 31 ◽  
pp. 380-381
Author(s):  
S.R. Allegra
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Ultrastructural Study ◽  
The Other ◽  
Blue Nevus ◽  
Normal Complement ◽  
Golgi Vesicles ◽  
Golgi System ◽  
The Subject ◽  
Cellular Blue Nevus

The respective roles of the ribo somes, endoplasmic reticulum, Golgi apparatus and perhaps nucleus in the synthesis and maturation of melanosomes is still the subject of some controversy. While the early melanosomes (premelanosomes) have been frequently demonstrated to originate as Golgi vesicles, it is undeniable that these structures can be formed in cells in which Golgi system is not found. This report was prompted by the findings in an essentially amelanotic human cellular blue nevus (melanocytoma) of two distinct lines of melanocytes one of which was devoid of any trace of Golgi apparatus while the other had normal complement of this organelle.

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.

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.

The Question of Relationship Between Golgi Vesicles and Synaptic Vesicles in Octopus Neurons

1970 ◽  
Vol 7 (1) ◽  
pp. 189-201
Author(s):  
E. G. GRAY
Keyword(s):  
Electron Microscopy ◽  
Golgi Apparatus ◽  
Frontal Lobe ◽  
Synaptic Vesicles ◽  
Optic Lobe ◽  
Visual Cell ◽  
Visual Cells ◽  
Golgi Vesicles

Electron microscopy of the vertical lobe of octopus brain shows that the synaptic knobs of axons with perikarya in the median superior frontal lobe have synaptic vesicles, approximately 28% of which are dense-cored (or granulated). In contrast, the endings of the amacrine neurons in the vertical lobe and the endings in the retina and optic lobe, both of which are derived from the retinal visual cells, have only agranular synaptic vesicles. The Golgi apparatuses of the median superior frontal perikarya have vesicles, approximately 4.3% of which are granulated. The amacrine Golgi apparatuses have 1.5% granulated vesicles. The visual cell Golgi apparatuses have virtually no dense-cored vesicles, only agranular ones. The question of the formation of dense-cored and agranular synaptic vesicles at the Golgi apparatus and their subsequent transport to the terminals are related to these observations.

Visualization of changes in ciliary tip configuration caused by sliding displacement of microtubules in macrocilia of the ctenophore Beroe

1985 ◽  
Vol 79 (1) ◽  
pp. 161-179 ◽  
Author(s):  
S.L. Tamm ◽  
S. Tamm
Keyword(s):  
Electron Microscopy ◽  
Dense Material ◽  
Bend Angle ◽  
Two Dimensional ◽  
Electron Dense Material ◽  
Central Pair ◽  
Rest Position ◽  
Recovery Stroke ◽  
Dimensional Models ◽  
As If

Macrocilia from the lips of the ctenophore Beroe consist of multiple rows of ciliary axonemes surrounded by a common membrane, with a giant capping structure at the tip. The cap is formed by extensions of the A and central-pair microtubules, which are bound together by electron-dense material into a pointed projection about 1.5 micron long. The tip undergoes visible changes in configuration during the beat cycle of macrocilia. In the rest position at the end of the effective stroke (+30 degrees total bend angle), there is no displacement between the tips of the axonemes, and the capping structure points straight into the stomach cavity. In the sigmoid arrest position at the end of the recovery stroke (−60 degrees total bend angle), the tip of the macrocilium is hook-shaped and points toward the stomach in the direction of the subsequent effective stroke. This change in tip configuration is caused by sliding displacement of microtubules that are bound together at their distal ends. Electron microscopy and two-dimensional models show that the singlet microtubule cap acts as if it were hinged to the ends of the axonemes and tilted to absorb the microtubule displacement that occurs during the recovery stroke. The straight and hooked shapes of the tip are thought to help the ctenophore ingest prey.

Origine et formation de différents types de vacuoles induites par la multiplication d'Alphavirus Sindbis dans divers systemes cellulaires

1979 ◽  
Vol 25 (12) ◽  
pp. 1452-1459 ◽  
Author(s):  
Yves Lombard ◽  
Philippe Poindron ◽  
Aimé Porte
Keyword(s):  
Endoplasmic Reticulum ◽  
Glial Cells ◽  
Chicken Embryo ◽  
Cytoplasmic Membrane ◽  
Dense Material ◽  
Newborn Mice ◽  
Electron Dense Material ◽  
Double Membrane ◽  
Single Membrane ◽  
Chicken Embryo Fibroblasts

Spherule-containing vacuoles and nucleocapsid-bearing vacuoles (cytopathic vacuoles types 1 and 2 respectively of Grimley et al. 1968) induced by Alphavirus Sindbis were studied in brains from newborn mice, chicken embryo fibroblasts, and two lines of tumoral glial cells from muridae. Endoplasmic reticulum (ER) elements and finely granular electron-dense material also seen in contact with nucleocapsids seemed to be involved in the formation of the classical single-membrane spherule-containing vacuoles. A second type of spherule-containing vacuoles were characterized by their double membrane and an amorphous electron-dense content and were probably derived from mitochondria. Nucleocapsid-bearing vacuoles were formed from modified ER elements and seemed to be linked to excessive synthesis of viral material. Such ER alterations were not observed in RG6 cells. In these cells, there were only spherule-containing vacuoles, while nucleocapsids were seen associated with the cytoplasmic membrane only.

The genetics, ultrastructure, and tubulin polypeptides of mebendazole-resistant mutants of Caenorhabditis elegans

1989 ◽  
Vol 67 (10) ◽  
pp. 2422-2431 ◽  
Author(s):  
Robin A. Woods ◽  
Kathleen M. B. Malone ◽  
Andrew M. Spence ◽  
Wade J. Sigurdson ◽  
Edward H. Byard
Keyword(s):  
Caenorhabditis Elegans ◽  
Dense Material ◽  
Autosomal Gene ◽  
Wild Type ◽  
Electron Dense Material ◽  
C Elegans ◽  
Accessory Cells ◽  
Ethylmethane Sulphonate ◽  
Resistant Mutants ◽  
Β Tubulin

Mebendazole-resistant mutants of Caenorhabditis elegans were isolated following mutagenesis of the wild-type strain, N2, with ethylmethane sulphonate. The mutants define a single autosomal gene and are allelic to ben-1. They grow, move, and reproduce normally in the presence of mebendazole and are cross-resistant to albendazole, cambendazole, fenbendazole, methylbenzimidazole carbamate, and thiabendazole. Accumulations of membrane-bound, electron-dense material associated with the nervous tissue and associated cells are seen in electron micrographs of L3, L4, and adult stages of N2 grown in the presence of mebendazole, but are not found in the mutants. The electron-dense material appears to be associated with the accessory cells of the neuropil rather than with the neurons. The tubulins from wild type, N2, and the mutants were characterised by two-dimensional electrophoresis followed by silver staining and Western blotting with monoclonal antibodies to α- and β-tubulin. A single isotype of α-tubulin is apparent in both N2 and the mutants. One major and three minor β-tubulin isotypes, bt-1 to bt-3, can be discerned in N2; the minor isotype bt-2 is absent in all the mutants. These findings suggest that the isotype bt-2 is the primary site of action of benzimidazole-based drugs in C. elegans.

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