The effects of high hydrostatic pressure on microfilaments and microtubules in Xenopus laevis

Development ◽  
1978 ◽  
Vol 44 (1) ◽  
pp. 281-295
Author(s):  
Paul-Emil Messier ◽  
C. Seguin
Keyword(s):  
Electron Microscopy ◽  
Hydrostatic Pressure ◽  
Xenopus Laevis ◽  
Cell Elongation ◽  
High Hydrostatic Pressure ◽  
Light And Electron Microscopy ◽  
Duration Of Treatment ◽  
Neuroepithelial Cells ◽  
Exerted Pressure ◽  
Xenopus Laevis Embryos

Xenopus laevis embryos of stages 14–20 were subjected, for periods of 5–330 min, to hydrostatic pressures ranging from 500 to 10000 psi. The specimens were fixed under corresponding pressures and their neuroepithelium was studied under light and electron microscopy. A pressure of 3000 psi, maintained for as long as 180 min, did not inhibit neurulation though it induced slight deformities of the neuroepithelium. A pressure of 4000 psi, applied for 180 min, disrupted the apical ring of microfilaments and blocked neurulation. The cells lost their dissymmetry. The effect was reversible. Lengthening the duration of treatment to 330 min caused the neuroepithelial cells to loose their microtubules and to become round. This situation was not reversible. Our results indicated that microfilaments are more sensitive than microtubules, that both organelles became increasingly sensitive as the exerted pressure was increased and that microtubules of older embryos exhibited a better resistance. Finally, we showed a correlation between the presence of microfilaments and the constricted state of the cellular apices and a relationship between the presence of microtubules and cell elongation.

Development of the optic nerve in Xenopus laevis

Development ◽  
1982 ◽  
Vol 72 (1) ◽  
pp. 225-249
Author(s):  
Charles Cima ◽  
Philip Grant
Keyword(s):  
Electron Microscopy ◽  
Optic Nerve ◽  
Xenopus Laevis ◽  
Ganglion Cell ◽  
Light And Electron Microscopy ◽  
Near Neighbour ◽  
Dorsoventral Axis ◽  
Fibre Size ◽  
Autoradiographic Analysis ◽  
Young Old

Development of the Xenopus laevis optic nerve was studied by light and electron microscopy from embryonic stage 26, before the retina has formed, to juveniles, 8 months post-metamorphic. Low-power EM photographs of sections through the retinal optic nerve (RON), middle optic nerve (MON) and chiasmatic optic nerve (CON) were prepared at different stages and the areas containing large axons (0·5 μm) were traced in optic nerve reconstructions. Ordering of fibre size along a dorsoventral axis was noted in the embryonic nerve, and this pattern persisted throughout development. Most large fibres, myelinated and unmyelinated, occupy an eccentric dorsocentral position in the MON while small axons are seen in a ventral peripheral crescent. In the CON, the dorsal one third to one half is occupied by large fibres while the ventral CON contains small fibres exclusively. If, as assumed, large axons are older than small axons (0·1–0·3 μm), then patterns of large and small axons along the nerve might reveal a chronotopic fibre ordering. Chronotopic ordering was confirmed by autoradiographic analysis of the distribution of old, labelled fibres and young, unlabelled newly arriving fibres in optic nerves between stage 51 and 57. The young—old labelling pattern corresponds to the small and large axon patterns respectively, in all sections of the optic nerve. Chronotopic ordering of fibres in the developing optic nerve can be explained, in part, by the dorsoventral asymmetric marginal growth of the developing retina and the phenomenon of fibre following as ganglion cell axons join near neighbour fascicles in the retina, converge at the optic disc and grow through the optic nerve.

scholarly journals Влияние температуры деформации в камере Бриджмена на особенности формирования дефектной структуры технически чистого титана

2018 ◽  
Vol 44 (20) ◽  
pp. 70
Author(s):  
Н.А. Шурыгина ◽  
А.М. Глезер ◽  
Д.Л. Дьяконов ◽  
А.А. Томчук ◽  
А.Г. Кадомцев ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Defect Structures ◽  
Cryogenic Temperatures ◽  
Two Phase ◽  
Α Phase ◽  
Electron Microscopy Data ◽  
Phase Mixture ◽  
Microscopy Data

AbstractTransmission electron microscopy data showed evidence of the formation of structural regions corresponding to deformation (dislocated) fragments and dynamically recrystallized grains in α-phase titanium upon torsion at high hydrostatic pressure at room and cryogenic temperatures. It is shown that the previously proposed “two-phase mixture” model is applicable to description of these defect structures.

An examination of the evidence for the existence of preformed pathways in the neural tube of Xenopus laevis

Development ◽  
1986 ◽  
Vol 91 (1) ◽  
pp. 181-195
Author(s):  
T. M. Scott ◽  
S. M. Bunt
Keyword(s):  
Electron Microscopy ◽  
Xenopus Laevis ◽  
Neural Tube ◽  
Branch Points ◽  
Intercellular Spaces ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Neuroepithelial Cells ◽  
Intercellular Clefts ◽  
Anatomical Guidance

We have examined the neural tube in Xenopus laevis tadpoles to investigate the anatomical guidance elements which may be present in the presumptive marginal zone. With appropriate fixation protocols the neuroepithelial cells appeared in contact; electron microscopic observations failed to show any specialized intercellular spaces preceding the growing axons. The first fibres were found in the intercellular clefts between the neuroepithelial cells near the surface of the neural tube. Reconstructions of the neural tube from examination of serial 1 µm sections showed that the intercellular clefts are non-aligned at this stage and branching. Scanning electron microscopy of the surface of the neural tube confirmed that the intercellular spaces are non-aligned and often branch caudal to the growing front of descending axons. Thus to grow in a consistent direction the developing axons may have to make consistent and selective (specific) selections of pathway at numerous branch points if their growth is restricted to these intercellular clefts. As more axons grow along the neural tube, the intercellular clefts become wider, and the neuroepithelial cells bounding the clefts become indented. At later stages many fibres were observed with both scanning and transmission electron microscopy to grow along the surface of the neural tube. These changes in neuroepithelial cell morphology and fibre pathway allow axons to form bundles which take a fairly straight course in contrast to the winding path which must be taken by the first axons to grow through the intercellular clefts.

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.

Development of the optic nerve in Xenopus laevis

Development ◽  
1982 ◽  
Vol 72 (1) ◽  
pp. 251-267
Author(s):  
Charles Cima ◽  
Philip Grant
Keyword(s):  
Electron Microscopy ◽  
Optic Nerve ◽  
Xenopus Laevis ◽  
Light And Electron Microscopy ◽  
Ependymal Cells ◽  
Glia Limitans ◽  
Nerve Development ◽  
Myelinated Fibres ◽  
Cytoplasmic Processes ◽  
Time Of Origin

We studied the time of origin, development and location of glial elements in the developing optic nerve of Xenopus with light and electron microscopy. The first cells acting as a primitive glia are ependymal cells lying dorsal to the chiasmatic optic nerve (CON) at Nieuwkoop & Faber (1956) NF stage 39. Later (stage 47/48), immature astrocyte cell bodies migrate from the periphery of the middle optic nerve (MON) into the central fibre mass along cytoplasmic processes extending from the outer glia limitans. Shortly thereafter, oligodendrocyte cell bodies appear in the centre of the fibre mass and myelination begins, first in the middle of the MON, spreading from the centre distally towards the chiasm and proximally to the retina. In late tadpoles myelinated fibres appear first in the CON then in the retinal optic nerve (RON) increasing markedly in juveniles and adults. Segment-specific patterns of glia and myelination appear during optic nerve development. During metamorphic climax, the ptic nerve shortens (Cullen & Webster, 1979), a process involving myelin and axon remodelling primarily in the MON. Neither the profound changes during metamorphosis, nor the processes of gliogenesis and myelination significantly alter the underlying chronotopic ordering in the tadpole nerve. In juvenile and adult optic nerves, however, as myelination and gliogenesis increase, and as more axons mature and grow in diameter, the dorsoventral chronotopic arrangement of axons becomes less apparent.

The effect of high hydrostatic pressure on Salmonella thompson and Listeria monocytogenes examined by electron microscopy

1994 ◽  
Vol 19 (6) ◽  
pp. 429-432 ◽  
Author(s):  
B.M. Mackey ◽  
K. Forestière ◽  
N.S. Isaacs ◽  
R. Stenning ◽  
B. Brooker
Keyword(s):  
Electron Microscopy ◽  
Listeria Monocytogenes ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure

Neural Fold Fusion in Xenopus Laevis Embryos

1974 ◽  
Vol 32 ◽  
pp. 282-283
Author(s):  
Linda L. Mak
Keyword(s):  
Electron Microscopy ◽  
Xenopus Laevis ◽  
Neural Tube ◽  
Morphological Study ◽  
Xenopus Laevis Embryos

A morphological study of neural fold fusion in neurulae of the African Clawed Toad Xenopus laevis was undertaken. Segments of neural folds were dissected from embryos at Nieuwkoop and Faber stages 18 (neural groove), 19 (neural fold fusion) and 20 (neural tube) and fixed for electron microscopy.Cells from specimens in the prefusion stage exhibited much vesicular activity, especially those lining the neural groove. In certain instances the vesicles were open, extruding organelles and cytoplasm into the neural groove. The membranous projections of these opened vesicles protruded into the extraembryonic space. Vesicles (v, Fig. 1) were arranged in rows below the surfaces of cells lying along the neural groove. Some vesicles appeared to coalesce to form larger ones.

scholarly journals Devitalizing Effect of High Hydrostatic Pressure on Human Cells—Influence on Cell Death in Osteoblasts and Chondrocytes

2020 ◽  
Vol 21 (11) ◽  
pp. 3836
Author(s):  
Janine Waletzko ◽  
Michael Dau ◽  
Anika Seyfarth ◽  
Armin Springer ◽  
Marcus Frank ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Cell Death ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Cell Damage ◽  
Water Soluble ◽  
Cartilage Tissue ◽  
Initial Assessment ◽  
Tetrazolium Salt ◽  
Tissue Samples

Chemical and physical processing of allografts is associated with a significant reduction in biomechanics. Therefore, treatment of tissue with high hydrostatic pressure (HHP) offers the possibility to devitalize tissue gently without changing biomechanical properties. To obtain an initial assessment of the effectiveness of HHP treatment, human osteoblasts and chondrocytes were treated with different HHPs (100–150 MPa, 250–300 MPa, 450–500 MPa). Devitalization efficiency was determined by analyzing the metabolic activity via WST-1(water-soluble tetrazolium salt) assay. The type of cell death was detected with an apoptosis/necrosis ELISA (enzyme-linked immune sorbent assay) and flow cytometry. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were carried out to detect the degree of cell destruction. After HHP treatment, the metabolic activities of both cell types decreased, whereas HHP of 250 MPa and higher resulted in metabolic inactivation. Further, the highest HHP range induced mostly necrosis while the lower HHP ranges induced apoptosis and necrosis equally. FESEM and TEM analyses of treated osteoblasts revealed pressure-dependent cell damage. In the present study, it could be proven that a pressure range of 250–300 MPa can be used for cell devitalization. However, in order to treat bone and cartilage tissue gently with HHP, the results of our cell experiments must be verified for tissue samples in future studies.

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