scholarly journals Electron-Lucent Plasma Membrane Layer

2020 ◽  
Author(s):  
Keyword(s):  
Plasma Membrane ◽  
Membrane Layer ◽  
Electron Lucent

The comparative ultrastructure of spermatozoa from Bothrimonus sturionis Duv. 1842 (Pseudophyllidea), Pseudanthobothrium hanseni Baer, 1956 (Tetraphyllidea), and Monoecocestus americanus Stiles, 1895 (Cyclophyllidea)

1984 ◽  
Vol 62 (6) ◽  
pp. 1059-1066 ◽  
Author(s):  
Barbara M. MacKinnon ◽  
Michael D. B. Burt
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Plasma Membrane ◽  
Main Body ◽  
Posterior Portion ◽  
Transmission Electron ◽  
Dense Nucleus ◽  
Comparative Ultrastructure ◽  
Electron Lucent ◽  
Mature Spermatozoa

The mature spermatozoa from Bothrimonus sturionis (Pseudophyllidea), Pseudanthobothrium hanseni (Tetraphyllidea), and Monoecocestus americanus (Cyclophyllidea) were examined using transmission electron microscopy. Transverse sections of the sperm of B. sturionis indicate that the number of sperm axonemes varies from one to eight, with approximately one-third of the sperm containing two axonemes. Likewise, the number of peripheral microtubules lying just within the external plasma membrane varies from 12 to 20. The nucleus is electron lucent and fibrous in appearance. The spermatozoa of B. sturionis show great variation in the material examined and the majority of them are believed to be aberrant. The spermatozoon of P. hanseni contains a single axoneme with the nucleus wrapped in a crescent around it in the anterior region of the sperm. The posterior portion of the spermatozoon is characterized by a helical flange which projects from the main body of the sperm. The spermatozoon of M. americanus is elongate and slender, containing a single axoneme with an electron-dense nucleus coiled around it in the anterior one-third of the sperm. Electron-opaque bodies, which may be glycogen, fill the cytoplasm. The spermatozoa of all three species contain neither an acrosome nor mitochondria. The flagella of all the spermatozoa have a 9 + "1" arrangement of microtubules. The importance of the ultrastructure of spermatozoa in the phylogeny and taxonomy of cestodes is discussed.

Electron Microscopy of California Isolate of Cat Leukemia Virus

1968 ◽  
Vol 26 ◽  
pp. 24-25
Author(s):  
T. G. Kawakami ◽  
G. H. Theilen ◽  
R. J. Munn
Keyword(s):  
Plasma Membrane ◽  
Developmental Stages ◽  
Leukemia Virus ◽  
Morphological Characteristics ◽  
Host Cells ◽  
Stage Of Development ◽  
Viral Particles ◽  
The Difference ◽  
Vacuolar Membranes ◽  
Electron Lucent

Although “C”-type viral particles have been observed in oats with feline leukemia, the developmental stages, morphological characteristics and sites of replication have not been fully described. The isolation of an agent from a cat with spontaneous leukemia and transmission of the disease with cell-free preparations to newborn kittens presented an opportunity for an extensive eleotron mioroscopic examination of the feline leukemogenic agent.The agent apparently undergoes development by budding from the plasma or vacuolar membranes of infected host cells. The earliest stage of development is recognizable in thin section by a crescent-shaped electron-dense zone beneath the plasma membrane (Fig. 1a). This structure or bud enlarges progressively into a sphere which is resolvable into two concentric components and concomitantly causes a protrusion of the plasma membrane. Later stages are independent of the host cell proper. The immature forms (Fig. 1b), one recently detached from the plasma membrane, still maintain the internal morphology of the later stages of budding but is completely surrounded by a protein coat. The mature forms (Fig. 2) which develop by reorganization of the dense shells possess either a central electron-dense or central electron-lucent nucleoid. The difference between mature electron-lucent and immature forms appears to be an absence of the organized concentric shell in the former.

Differentiated regions of human placental cell surface associated with exchange of materials between maternal and foetal blood: a new organelle and the binding of iron

1977 ◽  
Vol 25 (1) ◽  
pp. 279-291
Author(s):  
C.D. Ockleford ◽  
G. Menon
Keyword(s):  
Cell Surface ◽  
Amorphous Material ◽  
Iron Compound ◽  
Chorionic Villi ◽  
Membrane Layer ◽  
Transmission Electron ◽  
Innermost Layer ◽  
Thin Electron ◽  
Initial Binding ◽  
Electron Lucent

To elucidate the method of uptake of a neutral iron compound into the placenta, isolated human chorionic villi were incubated in a medium containing the substance and were fixed at intervals and subsequently examined using transmission electron microscopy. None of the specimens examined showed evidence of vesicular transport in either micro- or macro-pinocytic vesicles which were either coated or smooth-surfaced. Iron uptake may involve attachment of particles to differentiated regions of the cell surface of the syncytiotrophoblast. These differentiated zones in the syncytial cell surface are composed of morphological distinct parts and therefore probably merit classification as an organelle. Our interpretation of the organelle's structure is that it is flattened, with a maximum distance across of about 30 nm in the plane of the membrane. It is of otherwise uncertain shape but possesses a multilaminar structure. The external layer is apparently composed of the iron compound to be taken up. Beneath this is an electron-lucent layer possibly composed of glycoacalyx. The next innermost layer is continuous with the trilaminar unit membrane of the cell surface, however no trilaminar appearance is observed within the organelle. Beneath the membrane layer is an electron-dense plaque of amorphous material. Occasionally in favourable sections there is the suggestion of a thin electron-lucent strip interposed between the dense plaque and the membrane layer. The whole structure is composed therefore of 4 or 5 different regions. One possible function is that of initial binding in a process of active as opposed to passive transport of iron into the cell.

The local deletion of a microvillar cytoskeleton from photoreceptors of tipulid flies during membrane turnover

1982 ◽  
Vol 215 (1201) ◽  
pp. 469-479 ◽  
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Divalent Cation ◽  
Room Temperature ◽  
Membrane Turnover ◽  
Axial Filament ◽  
Thiol Protease ◽  
Intimate Association ◽  
Isolated Retina ◽  
Electron Lucent

The distal regions of the photoreceptor microvilli of tipulid flies are shed to extracellular space during membrane turnover. Before abscission, the microvillar tips undergo a transformation: they become deformed, and after conventional fixation for electron microscopy are relatively electron-lucent compared to the stable, basal microvillar segments. We now show that the electron-lucent segment is an empty bag of membrane whose P-face after freeze–etch preparation appears as densely particulate as the remainder of the microvillus. Transformation is achieved by the local deletion of a microvillar cytoskeleton which consists of a single, axial filament linked to the plasma membrane by side-arms. The filament may be partially preserved by the chelation of Ca 2+ ; the provision of a divalent cation (Mg 2+ or Ba 2+ ) stabilizes the side-arms during subsequent fixation, as has been shown previously for the rhabdomeral cytoskeleton of blowflies. Incubation of the isolated retina in the presence of 0.25 mM Ca 2+ at room temperature for 10–20 min causes proteolysis of the cytoskeleton which is blocked by as little as 0.5 mM of the thiol protease inhibitors Ep-475 and Ep-459. Loss of the cytoskeleton is accompanied by deform­ation of all regions of the microvilli. Local deletion of the cytoskeleton from the transformed zone of the normal rhabdom is sufficient to explain deformation of the microvillar tips, but not their subsequent abscission. The intimate association between a Ca 2+ -activated thiol protease and the cytoskeleton implied by the great rapidity of proteolysis calls for a reassessment of published studies of membrane turnover by radioauto­graphy, and of the nature of light-induced damage to arthropod photo­receptor membranes.

The role of the tegument of the metacercarial stage of Bucephalus haimeanus (Lacaze-Duthiers, 1854) in the absorption of particulate material and small molecules in solution

Parasitology ◽  
1979 ◽  
Vol 78 (1) ◽  
pp. 99-106 ◽  
Author(s):  
J. C. Higgins
Keyword(s):  
Plasma Membrane ◽  
Human Serum Albumin ◽  
Horseradish Peroxidase ◽  
Small Molecules ◽  
Particulate Material ◽  
Ruthenium Red ◽  
Tegumental Cell ◽  
Cytoplasmic Bridges ◽  
Electron Lucent

SUMMARYUptake by the tegument of metacercariae of Bucephalus haimeanus of both particulate material and small molecules in solution is demonstrated by the use of electron-dense tracers and autoradiographic techniques. Ruthenium red (RR) uptake involved pinocystosis and the formation of large, electron-lucent vesicles in the outer cytoplasmic tegument. RR lost its association with these vesicles and became freely dispersed within the cytoplasm as it passed through the outer cytoplasmic tegument, down the cytoplasmic bridges and into the tegumental cell bodies. Ferritin, iodinated insulin and iodinated human serum albumin were also located within the outer cytoplasmic tegument and ferritin collected beneath the inner plasma membrane of the outer cytoplasmic tegument. Horseradish peroxidase was not absorbed by the tegument although it bound strongly to the outer surface of the metacercariae. C-labelled glucose, phenylalanine, tryptophan and tyrosine were all detected in the outer cytoplasmic tegument.

Heterogeneity of Size and Distribution of Intramembrane Particles in the Plasma Membrane of Yeast

1977 ◽  
Vol 35 ◽  
pp. 596-597
Author(s):  
E. Keyhani
Keyword(s):  
Plasma Membrane ◽  
Candida Utilis ◽  
Synthetic Medium ◽  
Freeze Fracture ◽  
Translational Diffusion ◽  
Yeast Cells ◽  
Distilled Water ◽  
Intramembrane Particles ◽  
The Matrix ◽  
Water Cell

The matrix of biological membranes consists of a lipid bilayer into which proteins or protein aggregates are intercalated. Freeze-fracture techni- ques permit these proteins, perhaps in association with lipids, to be visualized in the hydrophobic regions of the membrane. Thus, numerous intramembrane particles (IMP) have been found on the fracture faces of membranes from a wide variety of cells (1-3). A recognized property of IMP is their tendency to form aggregates in response to changes in experi- mental conditions (4,5), perhaps as a result of translational diffusion through the viscous plane of the membrane. The purpose of this communica- tion is to describe the distribution and size of IMP in the plasma membrane of yeast (Candida utilis).Yeast cells (ATCC 8205) were grown in synthetic medium (6), and then harvested after 16 hours of culture, and washed twice in distilled water. Cell pellets were suspended in growth medium supplemented with 30% glycerol and incubated for 30 minutes at 0°C, centrifuged, and prepared for freeze-fracture, as described earlier (2,3).

Organization of the Pellicle and the Muciferous Glands in Euglena Gracilis

1970 ◽  
Vol 28 ◽  
pp. 104-105
Author(s):  
Hilton H. Mollenhauer ◽  
W. Evans
Keyword(s):  
Plasma Membrane ◽  
Euglena Gracilis ◽  
Complex Forms ◽  
Secondary Periodicity

The pellicular structure of Euglena gracilis consists of a series of relatively rigid strips (Fig. 1) composed of ridges and grooves which are helically oriented along the cell and which fuse together into a common junction at either end of the cell. The strips are predominantly protein and consist in part of a series of fibers about 50 Å in diameter spaced about 85 Å apart and with a secondary periodicity of about 450 Å. Microtubules are also present below each strip (Fig. 1) and are often considered as part of the pellicular complex. In addition, there may be another fibrous component near the base of the pellicle which has not yet been very well defined.The pellicular complex lies underneath the plasma membrane and entirely within the cell (Fig. 1). Each strip of the complex forms an overlapping junction with the adjacent strip along one side of each groove (Fig. 1), in such a way that a certain amount of sideways movement is possible between one strip and the next.

Localization of Sodium in Normal and Inhibited Transporting Epithelia

1971 ◽  
Vol 29 ◽  
pp. 392-393
Author(s):  
G. I. Kaye ◽  
J. D. Cole
Keyword(s):  
Plasma Membrane ◽  
Similar Pattern ◽  
Fixation Method ◽  
Colonic Epithelium ◽  
Gallbladder Epithelium ◽  
Rabbit Colon ◽  
Rabbit Gallbladder

For a number of years we have used an adaptation of Komnick's KSb(OH)6-OsO4 fixation method for the localization of sodium in tissues in order to study transporting epithelia under a number of different conditions. We have shown that in actively transporting rabbit gallbladder epithelium, large quantities of NaSb(OH)6 precipitate are found in the distended intercellular compartment, while localization of precipitate is confined to the inner side of the lateral plasma membrane in inactive gallbladder epithelium. A similar pattern of distribution of precipitate has been demonstrated in human and rabbit colon in active and inactive states and in the inactive colonic epithelium of hibernating frogs.

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