Showing papers on "Ultraviolet light published in 1968"

Changes in fluorescence, turbidity, and birefringence associated with nerve excitation.

Abstract: Various types of light sources were used during the course of the present experiments; an Osram quartz-iodine lamp operated at d-c 15 volts and approximately 150 watts was used in the later staage of the present study as a source of near-visible ultraviolet light. Quartz lenses L1 and L2 (Fig. 1) were used to condense the light on a 1-3-mm portion of the nerve. Optical filter F1, used to absorb visible light, was either a Corning glass filter (CS 7-83) or a Bausch and Lomb interference filter for 365 m,. Visible light emitted by the nerve was detected with a photomultiplier tube (RCA 4463) at a right angle to the direction of the incident light. Filter F2, used to absorb the incident light scattered by the nerve, was either a Corning filter CS 3-72 (transmitting visible light longer than 430 m,u in wavelength) or a Corning filter CS 5-75 (transmitting a narrow spectrum around

The isolation, genetics and survival characteristics of ultraviolet light-sensitive mutants in yeast

Abstract: 96 mutants of yeast have been isolated which were more sensitive than wild-type to ultraviolet irradiation. Genetic analysis showed that many are inherited as single mendelian recessive mutations, and that they occupy at lest 22 different loci. Survival curves show that in all the mutants the low UV-dose shoulder characteristic of the survival curve of wild-type yeast is absent or very reduced, but that the slopes vary from one mutant to the next and are often complex. 5 mutants are also more sensitive to ionising radiation than wild-type and 5 reduce the ability of yeast to sporulate.

Cell Division During Inhibition of Deoxyribonucleic Acid Synthesis in Escherichia coli

Abstract: When cultures of Escherichia coli B/r growing at various rates were exposed to ultraviolet light, mitomycin C, or nalidixic acid, deoxyribonucleic acid (DNA) synthesis stopped but cell division continued for at least 20 min. The chromosome configurations in the cells which divided were estimated by determining the rate of DNA synthesis during the division cycle. The cultures were pulse-labeled with 14C-thymidine, and the amount of label incorporated into cells of different ages was found by measuring the radioactivity in cells born subsequent to the labeling period. The cells which divided in the absence of DNA synthesis were those which had completed a round of chromosome replication prior to the treatments. It was concluded that completion of a round of replication is a necessary and sufficient condition of DNA synthesis for cell division.

Dark Recovery Processes in Escherichia coli Irradiated with Ultraviolet Light I. Effect of rec− Mutations on Liquid Holding Recovery

Abstract: We have examined various derivatives of Escherichia coli K-12 for liquid holding recovery, a type of recovery originally observed in E. coli B irradiated with ultraviolet light. Although most of the K-12 derivatives tested showed relatively little or no recovery under our conditions, four of the six independent rec(-) mutants examined, those carrying recA1, rec-12, recA13, and rec-56, respectively, displayed marked recovery. These mutants are distinguished from rec(+) strains by their increased sensitivity to ultraviolet radiation and decreased ability to undergo genetic recombination. Two of them have also been reported to release large amounts of their deoxyribonucleic acid as acid-soluble material, especially after irradiation. None of the three uvr(-) mutants examined, containing uvrA6, uvrB5, or uvrC34, showed comparable liquid holding recovery. The one rec(-) uvr(-) derivative tested, carrying recA13 and uvrA6, did not appear to undergo liquid holding recovery, although recA13 uvr(+) strains did. Genetic analysis of one strain, a recA13 mutant, indicated that all the rec(+) derivatives obtained from it by conjugation, transduction and reversion, had lost the property of showing liquid holding recovery. From these results, we conclude that in E. coli K-12 the expression of liquid holding recovery depends upon certain rec(-) mutations.

Thymine-Thymine Adduct as a Photoproduct of Thymine

Abstract: A product isolated from thymine irradiated with ultraviolet light in frozen aqueous solution undergoes dehydration on heating with acids. As judged by elemental analysis, mass, ultraviolet, infrared, and nuclear magnetic resonance spectra, the most probable structures for this compound and its dehydration product, respectively, are 5-hydroxy-6-4'-[5''-methylpyrimidin-2'-one]-dihydrothymine and 6-4'-[5'-methylpyrimidin-2'-one]-thymine. Apparently, this compound is a thymine-thymine adduct and presumably is formed through the rearrangement of an initial photoproduct. Both compounds are closely related to 6-4'-[pyrimidin-2'-one]-thymine which has been isolated from acid hydrolyzates of ultraviolet-irradiated DNA and supposedly is derived from cytosine-thymine adduct. Formation of such adducts between pyrimidine bases is apparently a common photoreaction and may be important to the study of the photochemistry and photobiology of nucleic acids.

Use of a Fluorescent Brightener to Demonstrate Cellulose in the Cellular Slime Molds

Abstract: The presence and location of cellulose in different stages of the life cycles of the cellular slime molds can be demonstrated by use of the disodium salt of 4,4′-bis(4-anilino-6-bis (2-hydroxyethyl)-amino-s-triazin-2-ylamino)-2,2′ -stilbene disulfonic acid, a fluorescent brightener. It may be used successfully as a direct stain at a concentration of 0.1% in half-normal saline at pH 6; and it may be incorporated into growth media as a vital stain at a concentration of 0.0025% with no inhibitory effect at any developmental stage. Vegetative myxamoebae contain no cellulose and show no fluorescence in the presence of this brightener when viewed with ultraviolet light. In later stages of the life cycle, the time and sites of cellulose formation can be demonstrated with the brightener because of its fluorescence. e.g., in the slime covering of the pseudoplasmodia, in the sorophore sheath, in the walls of stalk cells and spores, in the walls of microcysts, and in the walls and sheath material of macrocysts. The brightener appears to be a very sensitive indicator for cellulose, and it has certain advantages over other cellulose stains, since the staining reaction (fluorescence) is very intense, long-lasting, and not obscured by unstained cellulose-free myxamoebae if such are present.

Mutagenesis in Escherichia coli. II. Evidence for a common pathway for mutagenesis by ultraviolet light, ionizing radiation and thymine deprivation.

Abstract: Both thymine starvation and gamma radiation, like ultraviolet light, produce base change mutations to prototrophy in Escherichia coli and the Exr+ phenotype is involved in the mutagenic process. DNA strand breakage is a direct or indirect consequence of all three treatments suggesting that the filling of gaps in DNA by a process involving the exr gene product may be a common step in mutagenesis.

Surface Activities of Some North American Scorpions in Relation to Feeding

Abstract: Field and laboratory studies were conducted on the nocturnal surface activities any feeding behavior of scorpions, using ultraviolet light. Two species, Vejovis confusus and V. mesaensis, showed a decrease in surface occurrence as the evening progressed, while Centruroides sculpturatus showed a random occupation throughout the night. Increased intensity of moonlight resulted in a significant decrease in surface occurrence in V. confuses and V. mesaensis; C. sculpturatus showed no significant response to increased illumination. Species differences in the amount of surface activity and feeding behavior were noted. Potential prey, food preferences, and mechanisms used in prey detection are also discussed. See full-text article at JSTOR

Ultraviolet irradiation of mouse L cells: effects on DNA synthesis and progression through the cell cycle.

Abstract: Suspension cultures of mouse L cells were irradiated with ultraviolet light at exposures of 40, 100, and $200\ {\rm ergs}/{\rm mm}^{2}$ , which reduced the colony-forming ability of asynchronous cell populations to 95%, 70%, and 20% of the control value. The rate of DNA synthesis in irradiated cells was found to be temporarily depressed, but initiation of DNA synthesis as measured by entry of G1 phase cells to S phase was not inhibited. Cell populations irradiated in G1 or G2 phase showed no delay in their movement to S phase or to mitosis, respectively, but cell populations irridiated in S phase had a delay in their progression to G2 phase. Quantitative measurements showed that cell populations irradiated in late G1 or early S phase had a longer delay and a larger fraction of cells which failed to reach mitosis than cells irradiated in late S phase. The fraction of cells which failed to reach mitosis after irradiation was equal to the fraction of cells which lost their colony-forming ...

Protective immunity produced by the injection of x-irradiated sporozoites of Plasmodium berghei. II. Effects of radiation on sporozoites.

Abstract: The effects of X-radiation on the infectivity and development of sporozoites of Plasmodium berghei were determined. When susceptible mice were injected with X-irradiated sporozoites, results showed that the higher the dose of radiation, the smaller the percentage of mice that developed patent blood infections. Sporozoites irradiated with more than 10,000 rads failed to produce any blood infections. Small, but apparently mature, exoerythrocytic forms were found in the livers of rats that had been injected with X-irradiated sporozoites. Such forms were more numerous after a low dose of radiation, i.e., 2,000 rads, and were found to persist in the liver for at least 16 days after sporozoite injection. There may be a relationship between the presence of these forms and the protective immunity found in mice inoculated with irradiated sporozoites. Studies on the effects of ionizing radiations on parasitic protozoa have repeatedly shown that while an extremely high radiation dose is necessary to cause immediate death of the parasite, much lower doses can interfere with its infectivity (review by Kimball, 1955). Thus, doses of more than 100,000 roentgens (r) of X-rays were necessary to produce changes in motility in Trypanosoma gambiense in vitro, whereas a dose of 12,000 r abolished the infectivity of the trypanosome to mice (Halberstaedter, 1938). Although the immunogenicity of irradiated parasites, ranging from viruses (review by Luria, 1955) to helminths (I.A.E.A., 1964), has been investigated only a few such studies have been done with protozoa, e.g., Eimeria (Hein, in Urquhart, 1964), and Trypanosoma lewisi (Sanders and Wallace, 1966). These studies have shown that parasites irradiated with a dose which abolishes their reproductive potential and ability to produce patent infections may still retain their capacity to produce an immune response in a susceptible host. Much of the work on the effects of X-radiation on the malaria parasite has related primarily to the doses required to abolish the Received for publication 25 June 1968. * This work, contribution no. 430 from the Army Research Program on Malaria, was sponsored by the Commission on Malaria, Armed Forces Epidemiological Board, and was supported by the United States Army Medical Research and Development Command. t Department of Preventive Medicine. $ Department of Radiology. infectivity of the erythrocytic stages (Bennison and Coatney, 1945; Rigdon and Rudison, 1945; Ward, Bell, and Schneider, 1960; and Targett and Fulton, 1965), as well as the sporozoite stage (Bennison and Coatney, 1945). Ceithaml and Evans (1946) showed that erythrocytes parasitized by P. gallinaceum were capable of apparently normal oxygen uptake and glucose consumption after an X-ray dose sufficient to destroy reproductive capacity of the parasite (10,000 r). Only when the dose was increased to 30,000 r were these metabolic activities of the parasitized erythrocytes affected. The immunizing capability of X-irradiated erythrocytic stages of malaria parasites has been shown with P. gallinaceum (Ceithaml and Evans, 1946), and with P. berghei (Corradetti, Verolini, and Bucci, 1966; and Wellde and Sadun, 1967). P. gallinaceum sporozoites inactivated either with ultraviolet light or by drying were shown by Russell, Mulligan, and Mohan (1942) to be effective immunizing agents when injected into fowls. That such sporozoites might be more active agents of immunization than are inactivated erythrocytic parasites was suggested by the work of Richards (1966). Our own preliminary results (Nussenzweig et al., 1967) indicated the considerable protective effect induced by the injection of X-irradiated sporozoites of P. berghei into mice. The normal course of sporozoite-induced parasitemia in susceptible rodents, as well as quantitative aspects of the development of sporozoites into exoerythrocytic (E.E.) forms has been previously described (Vanderberg,

DEGRADATION OF THE DNA OF ESCHERICHIA COLI K12 REC- (JC1569b) AFTER IRRADIATION WITH ULTRAVIOLET LIGHT*

Abstract: — Degradation of the DNA of a rec- mutant of Escherichia coli K12 (JC1569 b) induced by u.v. light was investigated. The rate of degradation was much larger by growing bacteria than by stationary cells. When growing bacteria were starved for amino acids, their DNA became resistant to irradiation. The mode of u.v.-induced degradation was investigated by comparing the time course of release from the acid-insoluble fraction of the label for two growing cultures; the one was pulse-labeled with 3H-thymidine and the other was pulse-labeled and chased thereafter for 12 min. It was found that the label incorporated into the former culture begins to be lost from the acid-insoluble fraction prior to the loss of the label incorporated into the latter culture. It was concluded that breakdown of the replicating point precedes degradation of the bulk of the DNA. This result suggested that the replicating point is a sensitive site to irradiation and the u.v.-induced degradation of DNA seemed to be influenced by the state of chromosome at the time of irradiation. Experiments of centrifugation of lysed spheroplasts of bacteria uniformly labeled with 3H-thymidine in alkaline sucrose demonstrated that DNA of low molecular weight appeared after irradiation with only 5 ergs/ mm2, and that the molecular weight could not be restored by post-irradiation incubation. Considering these results, an hypothesis is proposed concerning the initiation of induced degradation of the DNA of the rec- mutant.

Oxidative phosphorylation in Escherichia coli.

Abstract: A particulate fraction obtained from sonic extracts of Escherichia coli was able to carry out oxidative phosphorylation with NADH2 as substrate and to perform the energy-dependent transhydrogenase reaction. The latter activity was more stable, suggesting that different coupling factors were involved in both systems. A coupling-factor preparation stimulated both reactions but to differing degrees. Oxidative phosphorylation was more sensitive than the transhydrogenase to irradiation with ultraviolet light, which destroyed a site located between flavin and cytochrome b1 in the respiratory chain. Experiments with dicumarol and pentachlorophenol suggested that these inhibitors and the coupling-factor preparation also interacted with the electron-transport chain at this site. Further evidence for the existence of two sites of energy coupling was obtained by the selective inhibition of the transhydrogenase by carbonyl cyanide m-chlorophenylhydrazone, EDTA, triiodothyronine, 2,4-dinitrophenol, and hydroxylamine. ...

Effect of nalidixic acid and hydroxyurea on division ability of Escherichia coli fil+ and lon- strains.

Abstract: Short periods of incubation in medium containing nalidixic acid or hydroxyurea, followed by a return to normal growth conditions, induced filament formation in Escherichia coli B (fil+) and AB1899NM (lon−) but not in B/r (fil−) and AB1157 (lon+). These drugs reversibly stopped deoxyribonucleic acid (DNA) synthesis with little or no effect on ribonucleic acid (RNA) synthesis or mass increase. The initial imbalance caused by incubation in these drugs was the same for B and B/r as was macromolecular synthesis following a return to normal growth conditions. DNA degradation caused by nalidixic acid was measured and found to be the same for B and B/r. Hydroxyurea caused no DNA degradation in these two strains. Survival curves as determined under various conditions by colony formation suggested that the property of filament formation was responsible for the extrasensitivity of fil+ and lon− strains to either nalidixic acid or hydroxyurea. E. coli B was more sensitive to either drug than was B/r or Bs-1. Pantoyl lactone or liquid holding treatment aided division and colony formation of nalidixic acid-treated B but had no effect on B/r. Likewise, the filament-former AB1899NM was more sensitive to nalidixic acid than was the non-filament-former AB1157. The sensitivity of B/r and Bs-1 to nalidixic acid was nearly the same except at longer times in nalidixic acid, when Bs-1 appeared more resistant. Even though nalidixic acid, hydroxyurea, and ultraviolet light may produce quite different molecular alterations in E. coli, they all cause a metabolic imbalance resulting in a lowered ratio of DNA to RNA and protein. We propose that it is this imbalance per se rather than any specific primary chemical or photochemical alterations which leads to filament formation by some genetically susceptible bacterial strains such as lon− and fil+.

Spontaneous and ICR191-A-induced Frameshift Mutations in the A Gene of Escherichia coli Tryptophan Synthetase

Abstract: Frameshift mutant trpA21 was isolated after ultraviolet treatment and frameshift mutant trpA540 after ICR191-A (an acridine derivative) treatment of wild-type Escherichia coli K-12 The A proteins of spontaneous and ICR191-A-induced partial revertants of these mutants contained altered amino acid sequences one residue shorter than the comparable sequence in the A protein of wild-type bacteria The data support the conclusion that ICR191-A causes frameshift mutations The findings further indicate that both base additions and deletions are elicited by ICR191-A treatment and that mutagenesis by this compound sometimes affects more than one base pair ICR191-A also weakly reverts some missense mutants Analyses of the relevant peptides of the purified A protein show single amino acid replacements compatible with single base-pair changes In addition, we found that some spontaneously revertible ICR191-A- and ultraviolet light-induced frameshift mutants are not further stimulated to revert by exposure to ultraviolet light

Evidence for a relationship between deoxyribonucleic acid metabolism and septum formation in Escherichia coli.

Abstract: Septum formation is a key step in bacterial division, but the mechanism which controls periodic septum formation is unknown. In an attempt to understand this mechanism, lon− mutants, in which septum formation is blocked by very doses of ultraviolet light (UV), were investigated. UV must act on some part of the apparatus of cytokinesis; thus, identification of the UV target would identify part of this apparatus. As likely possibilities, UV might damage the septum-forming site or it might damage deoxyribonucleic acid (DNA), since DNA replication is normally coordinated with septum formation. To distinguish between these possibilities, DNA was specifically sensitized by incorporating bromodeoxyuridine into lon− bacteria. These bacteria were strongly sensitized to longer wavelength UV (2,900 to 3,100 A) so that they failed to form septa, grew into filaments which lysed, and did not form colonies. Various control experiments supported the conclusion that UV inhibits septum formation as a result of alterations in DNA metabolism. A relationship thus exists between DNA metabolism and septum formation.

Ultraviolet-Induced Genetic Recombination in a Partially Diploid Strain of ESCHERICHIA COLI

Abstract: UNDERSTANDING the mechanism of genetic recombination is of prime concern to biologists. Breakage-reunion-type recombination events account for most, if not all, recombinant structures in bacteriophages h (MESELSON and WEIGLE 1961 ; KELLENBERGER, ZICHICHI and WEIGLE 1961; MESELSON 1964) and T4 (TOMIZAWA and ANRAKU 1964,1965; ANRAKU and TOMIZAWA 1965a, b; TOMIZAWA, ANRAKU and IWAMA 1966). These studies have also revealed the nature of some of the steps intermediate to recombinant formation. The genetic systems available in Escherichia coli K-12 are unusual in that they off er opportunities to study both reciprocal and nonreciprocal recombination events. Genetic ( TOMIZAWA 1960) and isotopic labeling ( OPPENHEIM and RILEY 1966) experiments have revealed some aspects of the recombination process following conjugal transfer of donor genetic material to recipient strains. However, problems concerned with replication of the donor chromosome during conjugation and vegetative chromosome replication in the recipient (CURTIS 1966) make complete analysis of recombination events following conjugation difficult. Therefore, it was decided to investigate recombination events in a partially diploid strain of E. coli K-12 (CURTISS 1962, 1964) in order to eliminate problems concerned with gene transfer. LEDERBERG, LEDERBERG, ZINDER and LIVELY (1951) and BECKHORN (see DEMEREC, WITKIN, BECKHORN, VISCONTI, FLINT, CAHN, COON, DOLLINGER, POWELL and SCHWARTZ 1951) showed that small doses of UV (ultraviolet light, 2537 A) would induce haploidization in partially diploid strains of E. coli K-12, but they did not study the kinetics of the process, since all surviving colonies still contained partially diploid cells. UV is known to stimulate genetic recombination in phage (JACOB and WOLLMAN 1955; HERSHEY 1958; LEVINE and CURTIS 196l), in E. coliK-12 (JACOB and WOLLMAN 1961), in yeast (ROMAN and JACOB 1958), and in the phage P22-Salmonella typhimurium transduction system (GAREN and ZINDER 1955). Thus, it was felt that the use of UV to stimulate genetic recombination in a partially diploid strain of E. coli K-12 ( CURTISS 1964) would provide a closed system, not involving gene transfer, with which meaningful results could be obtained. This communication reports findings on UV-induced haploidization, on recombination leading to homozygosity

Interaction of the exr and lon Genes in Escherichia coli

Abstract: Strains of Escherichia coli carrying the gene lon typically produced excess capsular polysaccharide, and were sensitive to ultraviolet light (UV) irradiation, thymine starvation, and nalidixic acid, forming long filaments after these treatments. Sensitivity was reduced by a number of posttreatments. In the presence of a second UV sensitivity gene, exr, some of these properties were suppressed: long filaments were not formed, the effect of lon on UV and nalidixic acid sensitivity was greatly reduced, and irradiation posttreatments gave an enhancement of survival characteristic of exr rather than lon strains. Production of capsular polysaccharide was not affected by the exr gene.

Genetic analysis of lon mutants of strain K-12 of Escherichia coli.

Abstract: Following UV irradiation of AB1157 31 mucoid ultraviolet light UV sensitive mutants were isolated. These were all induced to form filaments by UV irradiation, i.e. they had all the phenotypic properties of Lon mutants. These lon mutants fell into two phenotypic classes based on their sensitivity to UV. The gene determining UV sensitivity and mucoidy in all mutants of both Class A and Class B was cotransducible with proC. Intra-class crosses by Pl transduction yielded no UV resistant recombinants. Inter-class crosses yielded UV resistant nonmucoid recombinants, the frequency depending on the direction of the cross. The data imply two adjacent blocks in the lon region of E. coli and the order of markers in this region is probably proC tsx lon Class A lon purE Class B.

Responses of cultured Chinese hamster cells to ultraviolet light of different wavelengths.

Abstract: Cultured Chinese hamster cells responses to UV light of different wavelengths indicating photon absorbing molecules inhibition of colony development

Dark reactivation of damage induced by ultraviolet light in mammalian cells in vitro.

Abstract: INDUCTION of pyrimidine dimers in cellular DNA by irradiation with ultraviolet light and the molecular processes involved in the repair of this damage (photoreactivation1 and dark reactivation2–3) are established in bacteria, bacteriophage and transforming DNA. Investigations of the reactivation of ultraviolet-induced damage have been extended from micro-organisms to cover cultured mammalian cell lines4–6.