The influence of acridine dyes and caffeine on recovery from ultraviolet damage in Eudorina elegans

1975 ◽  
Vol 21 (11) ◽  
pp. 1849-1854 ◽  
Author(s):  
C. L. Kemp ◽  
K. M. Malloy
Keyword(s):  
Dna Synthesis ◽  
Acridine Orange ◽  
Ultraviolet Light ◽  
Ultraviolet Irradiation ◽  
Repair Process ◽  
Repair System ◽  
Acridine Dyes ◽  
Dark Survival ◽  
High Doses ◽  
Ultraviolet Damage

Caffeine and the acridine dyes, acridine orange and acriflavine, were used to examine the repair potential in Eudorina elegans following ultraviolet irradiation. Acridines blocked photoreactivation primarily as a result of absorption of photoreactivating wavelengths, but acridines did not influence dark survival. Therefore, an acridine-sensitive excision–resynthesis–repair process is absent in Eudorina.Caffeine decreased both dark and light survival, the latter only after relatively high doses of ultraviolet light were used for inactivation. The caffeine-sensitive repair process appears to function most actively when the organisms are engaged in DNA synthesis, indicating that a postreplication–repair system exists in Eudorina. However, the data suggest that a repair system not associated with the DNA synthetic phases may also exist.

scholarly journals SENSITIVITY OF MEIOTIC YEAST CELLS TO ULTRAVIOLET LIGHT

Genetics ◽  
1973 ◽  
Vol 73 (4) ◽  
pp. 531-541
Author(s):  
G Simchen ◽  
Y Salts ◽  
R Piñon
Keyword(s):  
Dna Repair ◽  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Uv Irradiation ◽  
Ultraviolet Irradiation ◽  
Meiotic Prophase ◽  
Yeast Cells ◽  
Repair System ◽  
Sporulation Medium ◽  
Sporulation Process

ABSTRACT Sporulating cells of Szccharomyces cereuisiae show an increasing sensitivity to ultraviolet irradiation. Maximum sensitivity is reached at a time comparable to meiotic prophase. Sensitivity is expressed as reduced sporulation after the irradiation. The uv effect can be efficiently reversed by photoreactivating light. Viability is also morc severely affected during premeiotic DNA synthesis and during meiosis than in earlier stages in sporulation. Cells left in sporulation medium after the irradiation show a reduced viability compared with the cells plated immediately after the irradiation. Non-sporulating diploids do not acquire sensitivity when exposed to sporulation medium, hence the sensitivity is related to the sporulation process. That meiosis itself is affected, rather than spore formation alone, is evident from experiments in which the uv irradiation interferes with the uncovering of a recessive marker and with commitment to meiosis. It is proposed that during meiotic prophase, the DNA repair system is different from that found in vegetative cells.

Effects of ultraviolet light on synchronized Chinese hamster ovary cells; potentiation by hydroxyurea

1977 ◽  
Vol 28 (1) ◽  
pp. 29-48
Author(s):  
K. Burg ◽  
A.R. Collins ◽  
R.T. Johnson
Keyword(s):  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Hela Cells ◽  
Chinese Hamster Ovary ◽  
Ultraviolet Irradiation ◽  
Chromosome Structure ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Ovary Cells

We have examined the effects of hydroxyurea on u.v.-irradiated Chinese hamster CHO-KI cells. Ultraviolet irradiation followed by incubation with hydroxyurea causes only slight disruption of DNA and chromosome structure in CHO-KI cells compared with HeLa cells. There is, however, a clear potentiation by hydroxyurea of the u.v. killing of CHO-KI cells, which is most pronounced at those points in the cycle which are reported to have small DNA precursor pools. This potentiation is reduced when DNA precursors are provided together with hydroxyurea. These data are discussed in terms of an uncoupling of excision and repair DNA synthesis.

Photoreactivation in Halobacterium cutirubrum

1972 ◽  
Vol 18 (7) ◽  
pp. 981-985 ◽  
Author(s):  
M. A. Hescox ◽  
D. M. Carlberg
Keyword(s):  
Energy Transfer ◽  
Natural Environment ◽  
Ultraviolet Irradiation ◽  
Halophilic Bacteria ◽  
Complete Recovery ◽  
Carotenoid Pigments ◽  
Original Population ◽  
High Doses ◽  
Ultraviolet Damage

Extremely halophilic bacteria are able to survive in a natural environment exposed to high doses of ultraviolet irradiation. One such organism, Halobacterium cutirubrum, has been characterized to possess an extremely efficient photoreactivation from ultraviolet damage. A population irradiated to 1% survivors can photoreactivate to complete recovery of the original population in less than 1 h of illumination. Inhibition of carotenoid pigments by 10−6 M diphenylamine decreased photoreactivation efficiency. The carotene pigments have been implicated in an energy-transfer role to augment the photoreactivation mechanism

scholarly journals Lesions induced in DNA by ultraviolet light are repaired at the nuclear cage

1984 ◽  
Vol 70 (1) ◽  
pp. 189-196
Author(s):  
S.J. McCready ◽  
P.R. Cook
Keyword(s):  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Hela Cells ◽  
Nuclear Matrix ◽  
Ultraviolet Irradiation ◽  
Mammalian Cells ◽  
Nuclear Dna ◽  
S Phase ◽  
Unscheduled Dna Synthesis ◽  
Phase Synthesis

In mammalian cells, S-phase DNA synthesis occurs at sites fixed to a sub-nuclear structure, the nuclear matrix or cage. This is an ordered network of non-histone proteins, which maintains its essential morphology even in the absence of DNA. We show here that unscheduled DNA synthesis following exposure of HeLa cells to ultraviolet light also takes place at this sub-structure. We also show that ultraviolet irradiation grossly reorganizes nuclear DNA, arresting S-phase synthesis at the cage and leaving the residual synthesis highly localized.

scholarly journals Lack of effect of metofluthrin and sodium phenobarbital on replicative DNA synthesis and Ki-67 mRNA expression in cultured human hepatocytes

2015 ◽  
Vol 4 (4) ◽  
pp. 901-913 ◽  
Author(s):  
Tomoya Yamada ◽  
Hiroko Kikumoto ◽  
Brian G. Lake ◽  
Satoshi Kawamura
Keyword(s):  
Dna Synthesis ◽  
Mrna Expression ◽  
Human Hepatocytes ◽  
Ki 67 ◽  
High Doses ◽  
Sodium Phenobarbital

High doses of metofluthrin have been shown to produce hepatocellular tumours in rats.

scholarly journals CYTOPLASMIC DNA SYNTHESIS IN AMOEBA PROTEUS

1962 ◽  
Vol 15 (3) ◽  
pp. 535-540 ◽  
Author(s):  
M. Rabinovitch ◽  
W. Plaut
Keyword(s):  
Nucleic Acid ◽  
Dna Synthesis ◽  
Acridine Orange ◽  
Particle Number ◽  
Amoeba Proteus ◽  
Acridine Orange Staining ◽  
Particle Population ◽  
Cell Age ◽  
Cytoplasmic Dna ◽  
Number Of Particles

Nucleic acid-containing particles in the cytoplasm of Amoeba proteus (cf. reference 1) were counted after acridine orange staining. The number of particles per ameba was found to be correlated with cell age and size. Fresh daughters had a mean particle number of 5400, whereas predivision amebae contained around 11,000 particles. Amebae from two other strains contained similar particles. The particles were found to be clustered in fasted cells and redispersed after feeding. A marked increase in the particle population was noted in anucleate fragments. These results, together with those previously presented, suggest that the particles multiply intracellularly. Their nature and their relationship to previous work on nucleic acid labeling in Amoeba are discussed.

Ultrastructural Changes in Euglena After Ultraviolet Irradiation

1973 ◽  
Vol 13 (3) ◽  
pp. 799-809
Author(s):  
A. MICHAELS ◽  
A. GIBOR
Keyword(s):  
Ultraviolet Light ◽  
Ultraviolet Irradiation ◽  
Euglena Gracilis ◽  
Structural Changes ◽  
Ultrastructural Changes ◽  
Electron Microscopic ◽  
Bleaching Process ◽  
In Cells

The structural changes associated with the ultraviolet-induced bleaching of light-grown cells of Euglena gracilis were investigated. Our light- and electron-microscopic observations of the bleaching process indicate that there is a continuity of plastid structure in cells 5 generations after receiving a bleaching dose of ultraviolet light. There seems to be a continuous dilution of the plastid thylakoids and a decrease in plastid size in the bleaching cells. There also seems to be a change in the position of the plastids in relation to the mitochondria in the bleaching cells. The plastids and possibly the mitochondria are the only organelles which are affected by the ultraviolet irradiation. The continuity of plastids in bleaching cells of Euglena is discussed in relation to the proposed effect of the ultraviolet light.

Stimulation of host DNA synthesis and induction of early antigens by ultraviolet light irradiated human cytomegalovirus

1978 ◽  
Vol 58 (4) ◽  
pp. 289-299 ◽  
Author(s):  
I. Boldogh ◽  
�. G�ncz�l ◽  
L. G�rtner ◽  
L. V�czi
Keyword(s):  
Dna Synthesis ◽  
Ultraviolet Light ◽  
Human Cytomegalovirus ◽  
Stimulation Of

PURE AND MOSAIC CLONES — A REFLECTION OF DIFFERENCES IN MECHANISMS OF MUTAGENESIS BY DIFFERENT AGENTS IN SACCHAROMYCES CEREVISIAE

1981 ◽  
Vol 23 (1) ◽  
pp. 73-79 ◽  
Author(s):  
A. Nasim ◽  
M. A. Hannan ◽  
Earle R. Nestmann
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ultraviolet Light ◽  
Nitrous Acid ◽  
Repair Process ◽  
Dna Lesions ◽  
Ethyl Methanesulfonate ◽  
Methyl Methanesulfonate ◽  
Mechanisms Of Mutagenesis ◽  
G1 Cells

The induction of pure and mosaic clones has been studied in haploid G1 cells of Saccharomyces cerevisiae. Following treatments with ultraviolet light, methyl methanesulfonate, ethyl methanesulfonate, nitrous acid, and N-methyl-N′-nitro-N-nitrosoguanidine, the relative proportions of pure mutant clones varied from 25 to 100% at comparable survival levels. Ultraviolet light and methyl methanesulfonate produced mainly pure mutant clones, whereas ethyl methanesulfonate and nitrous acid produced mainly mosaics at 59 to 100% survival levels. The ratio of pure to mosaic clones induced by nitrosoguanidine fell between these two classes. These results are consistent with a classification of mutagens on the basis of repair and replication-dependent mechanisms of mutagenesis in other organisms. Agents having actions similar to ultraviolet light may produce mainly pure clones through a pre-replicative process involving an error-prone DNA repair process. Others may produce mainly mosaic mutants due to the different nature of DNA lesions which may require a replication-dependent process for fixation of mutations. Preliminary data from combined treatments of mutagens belonging to two different classes (i.e. ultraviolet light and nitrous acid) suggest the possibility of an interaction between these agents, resulting in a higher proportion of pure clones, possibly due to an inducible process. Studies of induced frequencies of pure and mosaic clones may be useful in the characterization of mutagens with functional differences.

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