Ultraviolet radiation studies on the colonial alga, Eudorina elegans

1971 ◽  
Vol 17 (11) ◽  
pp. 1417-1424 ◽  
Author(s):  
C. L. Kemp ◽  
J. W. Wentworth
Keyword(s):  
Ultraviolet Radiation ◽  
Visible Light ◽  
Dna Synthesis ◽  
Ultraviolet Irradiation ◽  
Half Life ◽  
Deoxyribonucleic Acid ◽  
Multicellular Organism ◽  
Dark Repair ◽  
Complete Reversal ◽  
Survival Patterns

Eudorina elegans was used to examine the response of an easily manipulated, multicellular organism to ultraviolet irradiation. The results indicate that E. elegans possesses an efficient photoreversal process. It is capable of complete reversal of ultraviolet induced damage sufficient to inactivate 99.99% of the colony-forming ability of the organism. Eudorina loses the ability to respond to visible light reversal of ultraviolet-induced damage exponentially with time. The half-life of this loss is about 10 h at 32° and about 20 h at 22°. Postultraviolet temperature of incubation influences the surviving fraction with fewer survivors at 22° than at 32°. The survival patterns of E. elegans suggest that a specific dark repair of ultraviolet-induced lesions may not occur, but that some repair processes take place during cellular deoxyribonucleic acid (DNA) synthesis.

scholarly journals Evidence for the lack of deoxyribonucleic acid dark-repair in Halobacterium cutirubrum

1976 ◽  
Vol 156 (3) ◽  
pp. 569-575 ◽  
Author(s):  
V L Grey ◽  
P S Fitt
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Deoxyribonucleic Acid ◽  
Normal Growth ◽  
Dark Repair ◽  
Hybrid Dna

1. Halobacterium cutirubrum does not perform dark-repair of DNA either after u.v. irradiation or during normal growth. 2. Cultures irradiated with u.v. are readily photoreactivated, but do not recover viability in the dark. 3. No increase in the rate of DNA synthesis is observed in the surviving cells after u.v. irradiation. 4. At early times during normal semiconservative replication, newly incorporated thymidine is found only in the hybrid DNA. 5. It is suggested that these bacteria may be useful in the study of DNA replication and photoreactivation.

scholarly journals Fluorinated azobenzenes as supramolecular halogen-bonding building blocks

2019 ◽  
Vol 15 ◽  
pp. 2013-2019 ◽  
Author(s):  
Esther Nieland ◽  
Oliver Weingart ◽  
Bernd M Schmidt
Keyword(s):  
Solid State ◽  
Dft Calculations ◽  
Visible Light ◽  
Half Life ◽  
Photophysical Properties ◽  
Bathochromic Shift ◽  
Halogen Bonding ◽  
Building Blocks ◽  
Partial Overlap

ortho-Fluoroazobenzenes are a remarkable example of bistable photoswitches, addressable by visible light. Symmetrical, highly fluorinated azobenzenes bearing an iodine substituent in para-position were shown to be suitable supramolecular building blocks both in solution and in the solid state in combination with neutral halogen bonding acceptors, such as lutidines. Therefore, we investigate the photochemistry of a series of azobenzene photoswitches. Upon introduction of iodoethynyl groups, the halogen bonding donor properties are significantly strengthened in solution. However, the bathochromic shift of the π→π* band leads to a partial overlap with the n→π* band, making it slightly more difficult to address. The introduction of iodine substituents is furthermore accompanied with a diminishing thermal half-life. A series of three azobenzenes with different halogen bonding donor properties are discussed in relation to their changing photophysical properties, rationalized by DFT calculations.

scholarly journals Involvement of deoxyribonucleic acid polymerase β in nuclear deoxyribonucleic acid synthesis

1978 ◽  
Vol 173 (1) ◽  
pp. 309-314 ◽  
Author(s):  
T R Butt ◽  
W M Wood ◽  
E L McKay ◽  
R L P Adams
Keyword(s):  
Dna Synthesis ◽  
Dna Polymerase ◽  
Deoxyribonucleic Acid ◽  
Nuclear Dna ◽  
Dna Polymerase Beta ◽  
Cell Nuclei ◽  
High Molecular Weight Dna ◽  
Dna Polymerase Alpha ◽  
Polymerase Beta

The effects on DNA synthesis in vitro in mouse L929-cell nuclei of differential extraction of DNA polymerases alpha and beta were studied. Removal of all measurable DNA polymerase alpha and 20% of DNA polymerase beta leads to a 40% fall in the replicative DNA synthesis. Removal of 70% of DNA polymerase beta inhibits replicative synthesis by 80%. In all cases the nuclear DNA synthesis is sensitive to N-ethylmaleimide and aCTP (arabinosylcytosine triphosphate), though less so than DNA polymerase alpha. Addition of deoxyribonuclease I to the nuclear incubation leads to synthesis of high-molecular-weight DNA in a repair reaction. This occurs equally in nuclei from non-growing or S-phase cells. The former nuclei lack DNA polymerase alpha and the reaction reflects the sensitivity of DNA polymerase beta to inhibiton by N-ethylmaleimide and aCTP.

DEOXYCYTIDYLATE DEAMINASE LEVELS IN REGENERATING RAT LIVER

1961 ◽  
Vol 39 (6) ◽  
pp. 1043-1054 ◽  
Author(s):  
D. K. Myers ◽  
C. Anne Hemphill ◽  
Constance M. Townsend
Keyword(s):  
Dna Synthesis ◽  
Liver Regeneration ◽  
Partial Hepatectomy ◽  
Rat Liver ◽  
Deoxyribonucleic Acid ◽  
Regenerating Liver ◽  
Regenerating Rat Liver ◽  
High Level ◽  
Early Regeneration

Deoxycytidylate deaminase activity and net synthesis of deoxyribonucleic acid (DNA) in vivo were found to increase at approximately the same time during the early stages of liver regeneration. However, deaminase activity in the regenerating liver remained at a high level for 1 day after DNA synthesis had slowed down again during the later stages of regeneration. The increase in deaminase activity was restricted as a result of exposure to 600 r X radiation during early regeneration, but this effect only became evident 11–16 hours after the irradiation. Irradiation on the second day after partial hepatectomy, when deaminase levels in control regenerating livers were relatively constant, failed to affect the deaminase activity immediately but did produce a 40–50% decrease in activity 11–16 hours later. Other antimitotic agents, e.g., colchicine, had little effect on deaminase activity.

IN VIVO SYNTHESIS AND BREAKDOWN OF DEOXYRIBONUCLEIC ACID IN TRIBOLIUM CONFUSUM DUVAL

1966 ◽  
Vol 44 (12) ◽  
pp. 1571-1575 ◽  
Author(s):  
K. D. Chaudhary ◽  
A. Lemonde
Keyword(s):  
Dna Synthesis ◽  
Growth Phase ◽  
Deoxyribonucleic Acid ◽  
Total Concentration ◽  
Larval Growth ◽  
Pupal Stage ◽  
Larval Period ◽  
Tribolium Confusum ◽  
In Vivo Synthesis

The in vivo synthesis of deoxyribonucleic acid (DNA), as shown by the rate of incorporation of14C-thymidine, has been investigated at different stages in the life cycle of Tribolium confusum. During the larval period, a close similarity is observed between the rate of DNA synthesis and the pattern of growth. The pupal stage, which is a non-growth phase, is characterized by a cessation of DNA synthesis. During the larval growth phase, although the 3-day-old larvae have the lowest and the 13-day-old have the highest rate of DNA synthesis, the rate of DNA degradation in the older larvae is almost twice as great as that of the younger larvae. These findings are consistent with the observed total concentration of DNA of the insect at these stages.

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.

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.

HEALTH HAZARDS FROM MOBILE TOWER: A REVIEW

2021 ◽  
pp. 78-79
Author(s):  
Avni KP Skandhan ◽  
Skandhan KP ◽  
Prasad BS
Keyword(s):  
Ionizing Radiation ◽  
Ultraviolet Radiation ◽  
Visible Light ◽  
Mobile Phone ◽  
Gamma Rays ◽  
Health Hazards ◽  
X Rays ◽  
Radio Waves ◽  
Fm Radio ◽  
Smart Tv

Our knowledge on X-rays, gamma rays and ultraviolet radiation is ionising . Non-ionising gadget radiation is from Mobile Phone, Laptop, Tablet Smart TV etc. and harmful radiations is from mobile towers . FM radio waves, Microwaves, Visible light are also other forms of non-ionizing radiation.

Sign in / Sign up

Export Citation Format

Share Document