The ultrastructure of the epidermis of Diplectanum aequans (Monogenea)

Parasitology ◽  
1980 ◽  
Vol 80 (1) ◽  
pp. 9-21 ◽  
Author(s):  
M. K. Shaw
Keyword(s):  
Outer Membrane ◽  
Electron Density ◽  
Dense Material ◽  
Small Scale ◽  
Electron Dense Material ◽  
Granular Cytoplasm ◽  
Outer Epidermis

SummaryThe epidermis of Diplectanum aequans has, in general, been found to be similar to the epidermis of other monogeneans, consisting of a syncytial outer epidermis and sunken sub-epidermal nucleated regions. However, the epidermis of D. aequans differs from that of other monogeneans in 3 respects. These are, the presence of large areas of granular cytoplasm within the outer epidermis, the presence of myofibres invaginating into the epidermal matrix and, in the posterior regions of the epidermis, the presence of epidermal scales. These scales occur within the epidermal cytoplasm, beneath the outer membrane, and are composed of moderately electron-dense material. Also present beneath the outer membrane in the more anterior regions of the epidermis are small scale-like sclerites of a similar electron density to the epidermal scales.

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 Ultrastructural variations of the urothelial membrane in essential fatty acid (EFA)-deficient rats. A digital densitometric study.

1986 ◽  
Vol 34 (12) ◽  
pp. 1639-1644 ◽  
Author(s):  
F Kalinec ◽  
J H Calderón ◽  
B Monis
Keyword(s):  
Electron Density ◽  
Present Report ◽  
Dense Material ◽  
Transitional Epithelium ◽  
Unit Membrane ◽  
Experimental Conditions ◽  
Electron Dense Material ◽  
Outer Leaflet ◽  
Photodiode Array ◽  
Computer Controlled

The present report deals with a densitometric study of the ultrastructural images of the urothelial membrane of rats in the following experimental conditions: (1) EFA-deficient (EFAD) rats; (2) EFA-sufficient (EFAS) rats; and (3) EFAD rats that were fed the EFAD diet for 30 weeks and received an EFAS diet for the following 10 weeks (EFAD/S group). On electron micrographs of the transitional epithelium of ureters and urinary bladder of these rats, optical density (OD) profiles of the urothelial unit membrane were recorded and digitized using a computer-controlled microdensitometer with a solid-state self-scanned photodiode array sensor. A Gaussian curve was adopted as a model for the distribution of electron-dense material in each osmiophilic leaflet. Gaussian parameters were used to estimate the thickness of the urothelial membrane and of each osmiophilic leaflet, and the amount of electron-dense material and the maximal electron density present in each leaflet. In EFAS rats, the thick urothelial membrane was asymmetric like that of the normal, resulting from a greater thickness of the outer leaflet and a greater electron density of the cytoplasmic one. In EFAD rats, a loss of the characteristic ultrastructural asymmetry and a decrease of the total thickness of the unit membrane were detected. These changes were partially reversed in the EFAD/S rats.

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.

scholarly journals Developmental Changes in the Interference Reflectors and Colorations of Tiger Beetles (Cicindela)

1985 ◽  
Vol 117 (1) ◽  
pp. 111-117
Author(s):  
T. D. SCHULTZ ◽  
M. A. RANKIN
Keyword(s):  
Refractive Index ◽  
Electron Density ◽  
Dense Material ◽  
Developmental Changes ◽  
Dense Layer ◽  
Electron Dense Material ◽  
Interference Colour ◽  
Tiger Beetles ◽  
Colour Development

Samples of cicindelid cuticle were examined at various stages of adult ecdysis. The multilayered potential reflector was secreted in the initial stages of the moult, verifying that it is not tectocuticle and supporting the contention that it is a form of inner epicuticle. At early stages of ecdysis, the electron-dense layers were visible only when the section was post-stained. During post-ecdysial colour development, the dense layer increased in inherent electron density. Concurrently, the reflector increased in refractive index and the interference coloration increased in intensity and wavelength of maximum reflectance. Black pigment was also deposited simultaneously within the outer portion of the cuticle. It is proposed that electron-dense material was deposited in situ within the inner epicuticle after ecdysis, thereby increasing the wavelength and reflectance of interference colour.

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.

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.

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.

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.

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