Ultraviolet light inhibits grey crescent formation on the frog egg

1980 ◽  
Vol 189 (1) ◽  
pp. 73-76 ◽  
Author(s):  
Mario E. Manes ◽  
Richard P. Elinson
Keyword(s):  
Ultraviolet Light ◽  
Crescent Formation ◽  
Grey Crescent

Heat-shock-induced grey crescent formation in axolotl eggs and oocytes: the role of gravity

Development ◽  
1987 ◽  
Vol 100 (4) ◽  
pp. 599-609
Author(s):  
J.-C. Beetschen ◽  
J. Gautier
Keyword(s):  
Protein Synthesis ◽  
Heat Shock ◽  
Synergistic Action ◽  
Nuclear Factor ◽  
Crescent Formation ◽  
Animal Pole ◽  
Grey Crescent ◽  
Cytoskeletal Structure

Axolotl eggs were heat shocked (36.8°C, 10min) inside their jelly layers. Heat shock (HS) was shown to induce the precocious appearance of a grey crescent (GC) in a number of eggs immediately after fertilization (Benford & Namenwirth, 1974). It was also demonstrated that this phenomenon occurs in fertilized or artificially activated eggs only when they are shocked within 11/2h after spawning. The GC forms still later in heated unfertilized, nonactivated eggs. The role of the jelly layers is considered to be mechanical: a proportion of eggs is maintained in a tilted position until the egg is able to orient animal pole upwards under the influence of gravity as a late consequence of activation. The jelly layers are not essential if the eggs are artificially tilted or rotated during HS. GC formation can also be induced in in vitro maturing oocytes, provided they are tilted during HS. Gravity thus plays an essential role in the cytoplasmic rearrangements leading to HS-induced GC formation. Our results indicate a synergistic action between heat and gravity in this process. The cytological appearance of the GC formed in those experiments is that of a ‘Born's crescent’ with a conspicuous ‘vitelline wall’ (Pasteels, 1964). When oocytes are enucleated before maturation, HS has no effect on GC formation. A nuclear factor is therefore essential, as has been demonstrated in early GC formation induced by inhibitors of protein synthesis. Finally, incorporation of amino acids into oocyte proteins appears to be rapidly inhibited by HS (from 5 min). However, we cannot conclude that GC formation is in fact triggered by inhibition of protein synthesis. It is also likely that HS disrupts cytoskeletal structure, hence facilitating cytoplasmic rearrangements. Nevertheless, these results are in agreement with the scheme we recently proposed for GC formation in the rotated axolotl oocyte (Gautier & Beetschen, 1985).

Selective Inhibition of Cleavage in Different Regions of the Frog Egg by Sulphydryl Inhibitors

Development ◽  
1956 ◽  
Vol 4 (1) ◽  
pp. 73-92
Author(s):  
Lucena J. Barth
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Total Nitrogen ◽  
Selective Inhibition ◽  
Inorganic Materials ◽  
Crescent Formation ◽  
Animal Pole ◽  
Grey Crescent ◽  
Histochemical Methods ◽  
Small Spot

That the materials for protein synthesis in the frog egg must come from yolk is indicated by the constancy of total nitrogen during development (Gregg & Ballentine, 1946) and the fact that the egg can develop with no outside source of organic or inorganic materials. When and where in the developing egg new proteins arise, and what are the mechanisms which control the rate and direct the specificity of such syntheses, are problems which are beginning to occupy increasing numbers investigators using several methods of attack—immunological, enzymological, electrophoretic, and incorporation of labelled amino acids, for example. Brachet (1940), using histochemical methods, described a change in the distribution of sulphydryl proteins coincident with grey crescent formation. In the newly-laid egg of Triton or Pleurodeles Brachet found the sulphydryl proteins to be restricted to a small spot centred about the maturation figure near the animal pole. This picture changed during the first few hours after fertilization.

scholarly journals Ion currents and membrane domains in the cleaving Xenopus egg.

1983 ◽  
Vol 97 (6) ◽  
pp. 1753-1761 ◽  
Author(s):  
D Kline ◽  
K R Robinson ◽  
R Nuccitelli
Keyword(s):  
Outward Current ◽  
Cleavage Furrow ◽  
Ion Currents ◽  
Membrane Domains ◽  
Vibrating Probe ◽  
Crescent Formation ◽  
Grey Crescent ◽  
Inward Current ◽  
Channel Distribution ◽  
Xenopus Egg

We used an extracellular vibrating probe to measure ion currents through the cleaving Xenopus laevis egg. Measurements indicate sharp membrane heterogeneities. Current leaves the first cleavage furrow after new, unpigmented membrane is inserted. This outward current may be carried by K+ efflux. No direct involvement of the Na+,K+-ATPase in the generation of this outward current is detected at first cleavage. Inward current enters the old, pigmented membrane; however, it does not enter uniformly. The inward current is largest at the old membrane bordering the new membrane. This suggests a heterogeneous ion channel distribution within the old membrane. Experiments suggest that the inward current may be carried by Na+ influx, Ca2+ influx, and Cl- efflux. No steady currents were detected during grey crescent formation, the surface contraction waves preceding cleavage, or with groove formation at the beginning of cleavage.

The Use of Styrenes as Embedding Media for Electron Microscopy

1971 ◽  
Vol 29 ◽  
pp. 488-489
Author(s):  
Edward D. De-Lamater ◽  
Eric Johnson ◽  
Thad Schoen ◽  
Cecil Whitaker
Keyword(s):  
Electron Microscopy ◽  
Surface Tension ◽  
Ultraviolet Light ◽  
Methyl Ethyl Ketone Peroxide ◽  
Methyl Ethyl ◽  
Styrene Polymerization ◽  
Radical Initiation ◽  
Tertiary Butyl ◽  
Low Viscosity ◽  
Free Radical Initiation

Monomeric styrenes are demonstrated as excellent embedding media for electron microscopy. Monomeric styrene has extremely low viscosity and low surface tension (less than 1) affording extremely rapid penetration into the specimen. Spurr's Medium based on ERL-4206 (J.Ultra. Research 26, 31-43, 1969) is viscous, requiring gradual infiltration with increasing concentrations. Styrenes are soluble in alcohol and acetone thus fitting well into the usual dehydration procedures. Infiltration with styrene may be done directly following complete dehydration without dilution.Monomeric styrenes are usually inhibited from polymerization by a catechol, in this case, tertiary butyl catechol. Styrene polymerization is activated by Methyl Ethyl Ketone peroxide, a liquid, and probably acts by overcoming the inhibition of the catechol, acting as a source of free radical initiation.Polymerization is carried out either by a temperature of 60°C. or under ultraviolet light with wave lengths of 3400-4000 Engstroms; polymerization stops on removal from the ultraviolet light or heat and is therefore controlled by the length of exposure.

Resolution in photoelectron microscopy

1991 ◽  
Vol 49 ◽  
pp. 458-459
Author(s):  
G. F. Rempfer
Keyword(s):  
Electron Microscopy ◽  
Electric Field ◽  
Ultraviolet Light ◽  
Uniform Field ◽  
Virtual Image ◽  
Lens System ◽  
Photoemission Electron Microscopy ◽  
Planar Electrode ◽  
Electron Lens ◽  
Photoemission Electron

In photoelectron microscopy (PEM), also called photoemission electron microscopy (PEEM), the image is formed by electrons which have been liberated from the specimen by ultraviolet light. The electrons are accelerated by an electric field before being imaged by an electron lens system. The specimen is supported on a planar electrode (or the electrode itself may be the specimen), and the accelerating field is applied between the specimen, which serves as the cathode, and an anode. The accelerating field is essentially uniform except for microfields near the surface of the specimen and a diverging field near the anode aperture. The uniform field forms a virtual image of the specimen (virtual specimen) at unit lateral magnification, approximately twice as far from the anode as is the specimen. The diverging field at the anode aperture in turn forms a virtual image of the virtual specimen at magnification 2/3, at a distance from the anode of 4/3 the specimen distance. This demagnified virtual image is the object for the objective stage of the lens system.

Ultrastructural Changes in Three Different Mammalian Cells Following Ultraviolet Laser Irradiation

1972 ◽  
Vol 30 ◽  
pp. 350-351
Author(s):  
K. Shankar Narayan ◽  
Kailash C. Gupta ◽  
Tohru Okigaki
Keyword(s):  
Ultraviolet Light ◽  
Mammalian Cells ◽  
Biological Effects ◽  
Survival Rates ◽  
Chinese Hamster ◽  
Cell Types ◽  
Differential Sensitivity ◽  
Ultrastructural Changes ◽  
Ultraviolet Laser

The biological effects of short-wave ultraviolet light has generally been described in terms of changes in cell growth or survival rates and production of chromosomal aberrations. Ultrastructural changes following exposure of cells to ultraviolet light, particularly at 265 nm, have not been reported.We have developed a means of irradiating populations of cells grown in vitro to a monochromatic ultraviolet laser beam at a wavelength of 265 nm based on the method of Johnson. The cell types studies were: i) WI-38, a human diploid fibroblast; ii) CMP, a human adenocarcinoma cell line; and iii) Don C-II, a Chinese hamster fibroblast cell strain. The cells were exposed either in situ or in suspension to the ultraviolet laser (UVL) beam. Irradiated cell populations were studied either "immediately" or following growth for 1-8 days after irradiation.Differential sensitivity, as measured by survival rates were observed in the three cell types studied. Pattern of ultrastructural changes were also different in the three cell types.

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