scholarly journals The role of the centriolar region in animal cell mitosis. A laser microbeam study.

1977 ◽  
Vol 72 (2) ◽  
pp. 351-367 ◽  
Author(s):  
M W Berns ◽  
J B Rattner ◽  
S Brenner ◽  
S Meredith
Keyword(s):  
Animal Cell ◽  
Metaphase Plate ◽  
B Chromosome ◽  
Ultrastructural Analysis ◽  
Laser Microbeam ◽  
Membrane Breakdown ◽  
Pericentriolar Material ◽  
Ion Laser ◽  
Argon Ion

An argon ion laser microbeam (488 and 514 nm) was used to selectively irradiate one of the two centriolar regions of rat kangaroo Potorous tridactylis (PtK2) prophase cells in vitro. The cells were sensitized to the laser radiation by treatment with acridine orange (0.1-0.2 mug/ml). Ultrastructural examination of the irradiated centriolar regions demonstrated that the primary site of damage was the pericentriolar material. This result suggests that nucleic acid is present in the pericentriolar material. Behavioral and ultrastructural analysis demonstrated that cells with one damaged pericentriolar zone could undergo (a) nuclear membrane breakdown, (b) chromosome condensation, (c) metaphase plate formation, and (d) cytokinesis. However, the chromosomes neither separated nor exhibited any anaphase movements. Detailed ultrastructural analysis revealed the presence of kinetochore microtubules on both sides of chromosome mass and a lack of microtubules in the cytokinesis constriction. These results indicate that the pericentriolar material is important in spindle orgainization and essential for the formation of the interpolar microtubules.

scholarly journals Assembly properties of fluorescein-labeled tubulin in vitro before and after fluorescence bleaching.

1984 ◽  
Vol 99 (6) ◽  
pp. 2146-2156 ◽  
Author(s):  
R J Leslie ◽  
W M Saxton ◽  
T J Mitchison ◽  
B Neighbors ◽  
E D Salmon ◽  
...  
Keyword(s):  
Living Cells ◽  
Before And After ◽  
Ion Laser ◽  
Cross Links ◽  
Protein Incorporation ◽  
And Control ◽  
Argon Ion ◽  
Brain Tubulin ◽  
Control Protein

Brain tubulin has been conjugated with dichlorotriazinyl-aminofluorescein (DTAF) to form a visualizable complex for the study of tubulin dynamics in living cells. By using several assays we confirm the finding of Keith et al. (Keith, C. H., J. R. Feramisco, and M. Shelanski, 1981, J. Cell Biol., 88:234-240) that DTAF-tubulin polymerizes like control tubulin in vitro. The fluorescein moiety of the complex is readily bleached by the 488-nm line from an argon ion laser. When irradiations are performed over short times (less than 1 s) and in the presence of 2 mM glutathione, a mixture of DTAF-tubulin and control protein (as occurs after microinjection of the fluorescent conjugate into living cells) will retain full polymerization activity. Slow bleaching (approximately 5 min) or bleaching without glutathione promotes formation of covalent cross-links between neighboring polypeptides and kills the polymerization activity of DTAF-tubulin, including some molecules that are neither cross-linked nor bleached. Even under conditions that damage DTAF-tubulin, however, DTAF-microtubules are not destroyed by bleaching. They will continue to elongate by addition of DTAF-tubulin subunits to their free ends, and they neither bind nor exchange subunits along their lateral surfaces. These results suggest that DTAF-tubulin is a suitable analog for tubulin, both in studies of protein incorporation and for investigations of fluorescence redistribution after photobleaching.

Dynamic aspects of rhodamine dye photosensitization in vitro with an argon-ion Laser

1989 ◽  
Vol 9 (2) ◽  
pp. 83-89 ◽  
Author(s):  
Christopher R. Shea ◽  
Norah Chen ◽  
Tayyaba Hasan
Keyword(s):  
Argon Ion Laser ◽  
Ion Laser ◽  
Rhodamine Dye ◽  
Argon Ion

In vivo and in vitro instability of B chromosomes in palmarosa grass (Cymbopogon martinii var. motia)

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 966-973 ◽  
Author(s):  
H. L. Sreenath ◽  
K. S. Jagadishchandra
Keyword(s):  
Germ Line ◽  
Chromosome Instability ◽  
Metaphase Plate ◽  
B Chromosome ◽  
B Chromosomes ◽  
Dichlorophenoxyacetic Acid ◽  
Cymbopogon Martinii ◽  
2,4 Dichlorophenoxyacetic Acid

Meiotic and mitotic instability and elimination of B chromosomes was observed in diploid palmarosa (Cymbopogon martinii var. motia) with 2n = 20 + 1–2 B under in vivo and in vitro conditions. Under in vivo conditions B chromosomes were totally absent from the roots but preferentially transmitted in the germ line tissues. When present as a pair, the B chromosomes formed bivalents showing almost regular orientation, congression, and disjunction. When present singly, the B chromosome formed a univalent and did not pair with any of the A chromosomes and showed nonalignment on the metaphase plate during metaphase I. Immature inflorescences of a race of palmarosa with 2n = 20 + 2 B were cultured on Murashige and Skoog's medium containing 1 mg/L of 2,4-dichlorophenoxyacetic acid to produce embryogenic callus. The cytological analysis of the callus revealed only 20 A chromosomes in nearly all the cells, both the B chromosomes being eliminated. From this callus, plantlets without B chromosomes were regenerated on MS medium without growth regulators and established in the soil. The regenerated plants exhibited 20 A chromosomes with normal meiosis.Key words: Cymbopogon martinii, chromosome instability, palmarosa grass, B chromosomes, tissue culture, plant regeneration.

An Animal Protection Sponsor's View of MEIC

1997 ◽  
Vol 25 (3) ◽  
pp. 343-345
Author(s):  
Ethel Thurston
Keyword(s):  
Gold Standard ◽  
Animal Cell ◽  
Scientific Evidence ◽  
In Vitro Cytotoxicity ◽  
In Vitro Tests ◽  
Blood Concentrations ◽  
Animal Protection ◽  
Animal Tests ◽  
Lethal Blood

The Multicenter Evaluation of In Vitro Cytotoxicity programme is most important to animal protection, since it has validated 64 in vitro tests using advanced human data for 50 chemicals as the “gold standard”. Therefore, it has been able to compare animal cell tests, human cell tests and whole-animal tests fairly with unbiased scientific evidence. Added bonuses have included the identification and development of missing in vitro information (“missing tests”), publication of time-related lethal blood concentrations for all 50 chemicals, and some preliminary plans to resolve the 50,000 untested (or poorly tested) chemicals in the chemical mountain.

Laser Induced Etching for Generation of Si Nanocrystals and Spectroscopic Investigation of Morphology

2005 ◽  
Vol 23 ◽  
pp. 43-46
Author(s):  
H.S. Mavi ◽  
S. Rath ◽  
Arun Shukla
Keyword(s):  
Quantum Confinement ◽  
Silicon Nanocrystals ◽  
Laser Wavelength ◽  
Interconnected Network ◽  
Substrate Type ◽  
Argon Ion Laser ◽  
Si Nanocrystals ◽  
Ion Laser ◽  
Laser Induced Etching ◽  
Argon Ion

Laser-induced etching of silicon is used to generate silicon nanocrystals. The pore structure depends on the substrate type and etching laser wavelength. Porous silicon (PS) samples prepared by Nd:YAG laser (1.16 eV) etching of n-type substrate showed a fairly uniform and highly interconnected network of nearly circular pores separated by thin columnar boundaries, while no circular pits were produced by argon- ion laser (2.41 eV) etching under similar conditions. The size and size distribution of the nanocrystals are investigated by Raman and photoluminescence spectroscopies and analyzed within the framework of quantum confinement models.

A Current Conduction Mechanism in Laser Recrystallized Silicon Metal-Oxide-Semiconductor Transistors

1983 ◽  
Vol 23 ◽  
Author(s):  
Han-Sheng Lee
Keyword(s):  
Conduction Mechanism ◽  
Single Crystal Silicon ◽  
Silicon Films ◽  
Oxide Semiconductor ◽  
Silicon Substrates ◽  
Mos Transistors ◽  
Crystal Silicon ◽  
Ion Laser ◽  
Argon Ion ◽  
A Current

ABSTRACTN-channel MOS transistors were fabricated on silicon films that had been recrystallized by an argon ion laser at different power levels. These transistors showed electrical characteristics similar, but somewhat inferior to those devices fabricated on single crystal silicon substrates. These differences are attributed to the presence of trapping states at the grain boundaries of the crystallites in the recrystallized silicon. A coulombic scattering model is presented to explain these differences. In the case of films annealed at low laser power, an additional factor of nonuniform trap state distribution is invoked to explain device characteristics. This model provides an adequate explanation for the observed transport properties of transistors fabricated from recrystallized silicon films.

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