Morphogenetic analysis of changing cell associations following release of 2-cell and 4-cell mouse embryos from cleavage arrest

Development ◽  
1981 ◽  
Vol 61 (1) ◽  
pp. 331-345
Author(s):  
S. J. Kimber ◽  
M. A. H. Surani
Keyword(s):  
Electron Microscopy ◽  
Cell Division ◽  
Light And Electron Microscopy ◽  
Cytochalasin D ◽  
Mouse Embryos ◽  
Fresh Medium ◽  
The Other ◽  
Similar Process ◽  
Serial Sections ◽  
Morphogenetic Analysis

Two-cell and four-cell mouse embryos were cultured in Cytochalasin D (CD) for 40–48 h. They were fixed for light and electron microscopy at various times after washing off the CD. Cleavage-arrested embiyos in CD had well separated blastomeres but by 1 h from washing the embryos had compacted, in most cases without undergoing cell division. By 2 h after release from arrest one blastomere of the 2-cell arrested embryos had become crescent shaped and at 4–5 h the crescent-shaped blastomere had started to spread over the surface of the other rounded blastomere. This process continued until by 16–24 h from explantation to fresh medium one blastomere had almost completely engulfed the other. A similar process occurred in 4-cell arrested and released embryos. At this stage the embryos had accumulated fluid and become blastocyst-like vesicles. In 20% of 2-cell and 4-cell embryos one or two blastomeres underwent one cell division after release from arrest. Serial sections of these embryos lead to the conclusion that one or both progeny of the first cell to divide tended to be engulfed by the later dividing or non-dividing cell(s). These results are discussed in relation to the differentiation of ICM and trophectoderm in blastocysts.

Fine Structure of the Eye of a Nudibranch Mollusc, Hermissenda Crassicornis

1967 ◽  
Vol 2 (3) ◽  
pp. 349-358
Author(s):  
R. M. EAKIN ◽  
JANE A. WESTFALL ◽  
M. J. DENNIS
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Optic Nerve ◽  
Light And Electron Microscopy ◽  
The Other ◽  
Sensory Cells ◽  
Nerve Fibres ◽  
Supporting Cells ◽  
Small Bodies ◽  
Receptor Cells

The eye of a nudibranch, Hermissenda crassicornis, was studied by light and electron microscopy. Three kinds of cells were observed: large sensory cells, each bearing at one end an array of microvilli (rhabdomere) and at the other end an axon which leaves the eye by the optic nerve; large pigmented supporting cells; and small epithelial cells, mostly corneal. There are five sensory cells, and the same number of nerve fibres in the optic nerve. The receptor cells contain an abundance of small vesicles, 600-800 Å in diameter. The lens is a spheroidal mass of osmiophilic, finely granular material. A basal lamina and a capsule of connective tissue enclose the eye. In some animals the eye is ‘infected’ with very small bodies, 4-5 µ in diameter, thought to be symbionts.

Ultrastructure of region of a low safety factor in inhomogeneous giant axon of the cockroach

1976 ◽  
Vol 39 (4) ◽  
pp. 900-908 ◽  
Author(s):  
M. Castel ◽  
M. E. Spira ◽  
I. Parnas ◽  
Y. Yarom
Keyword(s):  
Electron Microscopy ◽  
Glial Cells ◽  
Extracellular Space ◽  
Light And Electron Microscopy ◽  
Giant Axon ◽  
Serial Sections ◽  
Giant Axons ◽  
Chemical Synapses ◽  
Cytoplasmic Processes ◽  
Periaxonal Space

1. The structure of the ventral giant axons of the cockroach at the level of ganglion T3 was studied by means of light and electron microscopy. 2. From serial sections and cobalt injections, the axons diameter was found to range between 40 and 60 mum at the caudal end of ganglion T3; toward the center of T3 they narrow to 20-40 mum, and again expand to 30-45 mum anteriorly in ganglion T3. 3. Each giant axon sends off several branches, 1-15 mum in diameter, into the neuropil. The giant axons and the bases of their branches are enveloped by cytoplasmic processes of glial cells. The periaxonal space is about 100-200 A. 4. Distally the branches are devoid of glial envelopes and the extracellular space between the branches and other axonal profiles is about 200 A. Terminals with presumptive chemical synapses on the giant axon branches were found. Clear vesicles, 300-400 A in diameter, are seen clustered together. The width of the supposedly synaptic gap is about 100 A. 5. In some areas the branches and other axonal profiles form close appositions.

Ultrastructure of eastern cottonwood clones susceptible or resistant to leaf rust

1987 ◽  
Vol 65 (8) ◽  
pp. 1586-1598 ◽  
Author(s):  
L. Shain ◽  
U. Järlfors
Keyword(s):  
Electron Microscopy ◽  
Leaf Rust ◽  
Light And Electron Microscopy ◽  
Infection Process ◽  
The Other ◽  
Host Cells ◽  
Eastern Cottonwood ◽  
Melampsora Medusae ◽  
Wall Appositions ◽  
Infected Cells

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused by Melampsora medusae was studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.

Asci of the Pezizales. I. The apical apparatus of iodine-positive species

1978 ◽  
Vol 56 (16) ◽  
pp. 1860-1875 ◽  
Author(s):  
Don A. Samuelson
Keyword(s):  
Electron Microscopy ◽  
Positive Reaction ◽  
Light And Electron Microscopy ◽  
The Other ◽  
Reaction Site ◽  
Lower Region

Morphological, developmental, and cytochemical studies on the apical apparatuses of five species, i.e., Peziza succosa, Ascobolus crenulatus, Saccobolus depauperatus, Thecotheus pelletieri, and Iodophanus granulipolaris, were performed with light and electron microscopy. Asci of all species, except A. crenulatus, stain blue in Melzer's reagent. The site of the iodine-positive reaction is believed to be an exogenous mucilaginous coat in P. succosa, S. depauperatus, and T. pelletieri. In I. granulipolaris, the reaction site appears to be the ascal wall. The presence of an annular indentation was found in the ascal tips of all species except I. granulipolaris. A line of dehiscence was found in the lower region of the annular indentation in T. pelletieri and S. depauperatus. The development of the apical apparatuses of all species occurs during and after late ascosporogenesis. The apical apparatus of I. granulipolaris diverged significantly in morphology and cytochemistry from the other species.

A Light and Electron Microscopic Study in Serial Sections of Skeletal and Extraocular Muscles in Mouse Myotonic Dystrophy

1974 ◽  
Vol 32 ◽  
pp. 6-7
Author(s):  
Bruce R. Pachter ◽  
Jacob Davidowitz ◽  
Goodwin M. Breinin
Keyword(s):  
Electron Microscopy ◽  
Animal Model ◽  
Myotonic Dystrophy ◽  
Skeletal Muscles ◽  
Light And Electron Microscopy ◽  
Hereditary Disease ◽  
Serial Sections ◽  
Electron Microscopic ◽  
Suitable Animal Model ◽  
Model Mouse

A suitable animal model (Mouse Strain Re-129 dy2j/dy2j) has been reported for myotonic dystrophy, a hereditary disease in which skeletal muscles degenerate. In the present study, another strain of mouse (Bar Harbor Strain C57BL/6J dy2j/dy2j), carrying this same myotonic gene (dy2j) was studied by light and electron microscopy (EM) in serial sections of epon embedded tissue.

Techniques Involved in the Acquisition of Serial Sections of the Atrioventricular Node for Light and Electron Microscopy

1968 ◽  
Vol 26 ◽  
pp. 226-227
Author(s):  
Sheila S. Emmett ◽  
J. C. Thaemert
Keyword(s):  
Electron Microscopy ◽  
Osmium Tetroxide ◽  
Light And Electron Microscopy ◽  
Atrioventricular Node ◽  
Electron Microscopic Level ◽  
Serial Sections ◽  
Electron Microscopic ◽  
Trapezoidal Shape ◽  
Old Mice

The acquisition of serial sections of the atrioventricular node for light and electron microscopy is a formidable task. Ordinary techniques are not adequate if the best possible results are to be achieved at the electron microscopic level. The techniques outlined below have proven to be valuable in locating and determining the position of the AV node.Whole hearts of 2-week old mice were fixed, in situ, by perfusion with 1% phosphate-buffered osmium tetroxide. The hearts were removed from the animals, sectioned transversely into 3 slices approximately equal in thickness, dehydrated in graded concentrations of ethanol and embedded in Epon 812. The block faces were trimmed to a trapezoidal shape ranging in size from 0.75 x 1 mm to 4 x 5 mm. Serial sections approximately 2 microns in thickness were cut with glass knives on a Porter-Blum MT-2 Ultramicrotome. While floating on a drop of water on the knife, each section was stretched with 1 drop of a 1:1, xylene in chloroform mixture applied directly to the section. The sections were picked up individually with a brush, transferred to a glass slide and oven dried for several hours prior to staining.

scholarly journals Morphological evidence by scanning electron microscopy of excretion of metacyclic forms of Trypanosoma cruzi in vector's urine

1988 ◽  
Vol 83 (3) ◽  
pp. 361-365 ◽  
Author(s):  
Rodrigo Zeledon ◽  
Rodolfo Bolaños ◽  
M. R. Espejo Navarro ◽  
Miguel Rojas
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Cell Division ◽  
Trypanosoma Cruzi ◽  
Urine Flow ◽  
The Other ◽  
Rectal Gland ◽  
Morphological Evidence ◽  
Different Levels ◽  
Scanning Electron

Comparision by scanning electron microscopy (SEM) of Trypanosoma cruzi flagellates attached to the cuticle of the rectal gland of infected Dipetalogaster maxima nymphs, showed marked differences before amd after feeding. Before feeding numerous metacyclic trypomastigotes were observed among the abundant epimastigotes that formed the carpet of flagellates. On the other hand, in insects that were allowed to urinate for 24 hours after a meal, the metacyclics were scarce,indicating that they had been detached by the urine flow. An asymetric type of cell division, probably originating both an epi-and a trypomastigote, was occasionally observed. The occurrence of swellings at different levels of the flagella of epimastigotes suggests that secondary sites of attachment may be common.

Somatic mitosis in Erysiphe graminis hordei

1972 ◽  
Vol 18 (12) ◽  
pp. 1915-1922 ◽  
Author(s):  
W. E. McKeen
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Nuclear Membrane ◽  
Osmium Tetroxide ◽  
Central Body ◽  
Nuclear Division ◽  
Light And Electron Microscopy ◽  
Erysiphe Graminis ◽  
The Other ◽  
Erysiphe Graminis Hordei

Somatic nuclear division in Erysiphe graminis hordei was studied by light and electron microscopy after various fixation and staining procedures. Electron microscopy studies of alcohol – acetic acid fixed material aided in providing an understanding of nuclear division and showing the gross alterations which occurred. Light microscopy indicated that a central body was always present at a specific site on the nuclear membrane in the interphase nucleus and was connected to chromatic spherical bodies. Microtubules were preserved when a short glutaraldehyde – osmium tetroxide fixation was used. Some microtubules extend from plaque to plaque while others terminate in kinetochores. A microtubular spindle, oblique to the nuclear and mildew-cells axes formed within the nuclear membrane. Typical prophases, metaphases, anaphases, and telophases were observed. Then one set of daughter chromatids bypassed the nucleolus which persisted intranuclearly until the daughter nuclei reached their destination, and the other set of daughter chromatids moved to midpoint in the other daughter cell. A narrow corridor, which connected daughter nuclei for some time, was filled mainly with microtubules and probably was the filament which was observed in the nucleus by light microscopy during nuclear division. At least six chromosomes were present in each nucleus.

Unusual macromorphology of the ductuli efferentes and epididymis of the koala (Phascolarctos cinereus)

2000 ◽  
Vol 48 (6) ◽  
pp. 681
Author(s):  
Rachel J. Gibson ◽  
Chris M. Leigh ◽  
William G. Breed
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Secretory Activity ◽  
The Other ◽  
Ciliated Cells ◽  
Phascolarctos Cinereus ◽  
Ductuli Efferentes ◽  
Sds Page ◽  
Marsupial Species ◽  
Electron Lucent

The macromorphology of the ductuli efferentes and epididymis of the koala (Phascolarctos cinereus) was investigated and found to differ from that of other marsupial species that have been described as it comprised four macroscopically distinct lobes. Light and electron microscopy of epithelium of the duct within these lobes showed that there were principal and ciliated cells lining the duct of the first lobe, indicating it to be composed of ductuli efferentes. In the other three lobes, the epithelium contained principal, basal, electron-lucent, and mitochondria-rich cells, showing that these three lobes included the epithelium of the epididymis. The height of this epithelium gradually increased along the duct (contrary to the situation in most other species that have been studied, in which a decrease occurs). Preliminary 1D-SDS PAGE observations of flushes from the caput and cauda epididymides suggested that epididymal proteins were secreted along much of the length of the duct; the greater height of the cauda epithelium may relate to the greater protein synthetic and secretory activity in this region.

scholarly journals The Effect of 5-Fluorouracil on the Growth and Nucleolus of Wheat Coleoptiles

1970 ◽  
Vol 23 (3) ◽  
pp. 561 ◽  
Author(s):  
RJ Rose ◽  
Jeanette Gregory ◽  
FV Mercer
Keyword(s):  
Electron Microscopy ◽  
Cell Division ◽  
Cell Elongation ◽  
Normal Cell ◽  
Light And Electron Microscopy ◽  
Wheat Coleoptile ◽  
Ribosome Synthesis ◽  
Cell Division Inhibition

Intact etiolated wheat coleoptiles grown from the beginning of imbibition III 5-fluorouracil (5-FU) show normal cell elongation, but division is inhibited. 5-FU-treated coleoptiles, 48 hr after imbibition, have enlarged nucleoli (165% increase in volume) in which the RNA is mostly confined to the periphery. Untreated and treated nucleoli were studied by light and electron microscopy. The 5-FU effects on the nucleolus, which occur at the time cell division usually occurs if 5-FU is not present, are of interest in relation to ribosome synthesis. Uracil or thymidine did not reverse the nucleolar effects, but uracil further inhibited growth, while thymidine partly reversed the cell division inhibition. Results with 5-FU and thymidine suggest that the coleoptile cells can divide at least once when they have abnormal nucleoli, but normal nucleolar metabolism is essential for the complete growth of the etiolated wheat coleoptile.

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