scholarly journals HETEROZYGOUS EFFECTS OF IRRADIATED CHROMOSOMES ON VIABILITY IN DROSOPHILA MELANOGASTER

Genetics ◽  
1976 ◽  
Vol 84 (2) ◽  
pp. 353-374
Author(s):  
Michael J Simmons
Keyword(s):  
Drosophila Melanogaster ◽  
Genetic Background ◽  
Genetic Component ◽  
X Rays ◽  
Heterozygous Condition ◽  
X Ray ◽  
Inversion Technique ◽  
High Doses

ABSTRACT Two large experiments were conducted in order to evaluate the heterozygous effects of irradiated chromosomes on viability. Mutations were accumulated on several hundred second chromosomes by delivering doses of 2,500r over either two or four generations for total X-ray exposures of 5,000r or 10,000r. Chromosomes treated with 5,000r were screened for lethals after the first treatment, and surviving nonlethals were used to generate families of fully treated chromosomes. The members of these families shared the effects of the first irradiation, but differed with respect to those of the second. The chromosomes treated with 10,000r were not grouped into families since mutations were accumulated independently on each chromosome in that experiment. Heterozygous effects on viability of the irradiated chromosomes were tested in both isogenic (homozygous) and nonisogenic (heterozygous) genetic backgrounds. In conjunction with these tests, homozygous viabilities were determined by the marked-inversion technique. This permitted a separation of the irradiated chromosomes into those which were drastic when made homozygous and those which were not. The results indicate that drastic chromosomes have deleterious effects in heterozygous condition, since viability was reduced by 2-4% in tests performed with the 10,000r chromosomes, and by 1% in those involving the 5,000r material. Within a series of tests, the effects were more pronounced when the genetic background was homozygous. Nondrastic irradiated chromosomes did not show detectable heterozygous effects. They also showed no homozygous effects when compared to a sample of untreated controls. In addition, there was no evidence for an induced genetic component of variance with respect to viability in these chromosomes. These results suggest that the mutants induced by high doses of X-rays are principally drastic ones which show deleterious effects on viability in heterozygous condition.

scholarly journals Is Micro X-ray Computer Tomography a Suitable Non-Destructive Method for the Characterisation of Dental Materials?

Polymers ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1271
Author(s):  
Andreas Koenig ◽  
Leonie Schmohl ◽  
Johannes Scheffler ◽  
Florian Fuchs ◽  
Michaela Schulz-Siegmund ◽  
...  
Keyword(s):  
Flexural Strength ◽  
Computer Tomography ◽  
Mechanical Performance ◽  
Dental Materials ◽  
Three Dimensional ◽  
X Rays ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Multiple Measurements ◽  
High Doses

The aim of the study was to investigate the effect of X-rays used in micro X-ray computer tomography (µXCT) on the mechanical performance and microstructure of a variety of dental materials. Standardised bending beams (2 × 2 × 25 mm3) were forwarded to irradiation with an industrial tomograph. Using three-dimensional datasets, the porosity of the materials was quantified and flexural strength was investigated prior to and after irradiation. The thermal properties of irradiated and unirradiated materials were analysed and compared by means of differential scanning calorimetry (DSC). Single µXCT measurements led to a significant decrease in flexural strength of polycarbonate with acrylnitril-butadien-styrol (PC-ABS). No significant influence in flexural strength was identified for resin-based composites (RBCs), poly(methyl methacrylate) (PMMA), and zinc phosphate cement (HAR) after a single irradiation by measurement. However, DSC results suggest that changes in the microstructure of PMMA are possible with increasing radiation doses (multiple measurements, longer measurements, higher output power from the X-ray tube). In summary, it must be assumed that X-ray radiation during µXCT measurement at high doses can lead to changes in the structure and properties of certain polymers.

IX. Nucleinsäuregehalt und Nucleinsäuresynthese nach Röntgenbestrahlung

1966 ◽  
Vol 21 (10) ◽  
pp. 960-966 ◽  
Author(s):  
Yasuhiko Takamori ◽  
Ernst-Randolf Lochmann ◽  
Wolfgang Laskowski
Keyword(s):  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Small Difference ◽  
Dry Weight ◽  
Nucleic Acid Content ◽  
X Rays ◽  
X Ray ◽  
Dna And Rna ◽  
High Doses ◽  
Different Doses

The amount of DNA and RNA per dry weight as well as the rate of RNA synthesis was determined in a series of almost isogenic and homozygous Saccharomyces strains of different ploidy which had irradiated with different doses of X-rays.It was found that the RNA content per dry weight showed only a small decrease after irradiation even with high doses. The decrease in the DNA content after irradiation is larger, and it is already maximal at the smallest X-ray dose tested (75 krad) . No further decrease could be observed even after application of 225 krad.The RNA synthesis is much more radioresistant in all strains tested (haploid-hexaploid) than the colony forming ability. X-ray doses which reduce the colony forming ability of the cells to less than 1% lead to a reduction of the RNA synthesis of only about 50 per cent. The inactivation of RNA synthesis increases with increasing irradiation doses and increasing incubation time after irradiation.There was only a small difference in the radiosensitivity of the synthesis of soluble or ribosomal RNA.Genetic effects on the radiation inactivation of the colony forming ability, previously described as “aα-effect” and “AS-effect”, show no influence on the radiosensitivity of cellular nucleic acid content and synthesis.

scholarly journals REPAIR REPLICATION AND PHOTOREPAIR OF DNA IN LARVAE OF DROSOPHILA MELANOGASTER

Genetics ◽  
1974 ◽  
Vol 77 (4) ◽  
pp. 687-700
Author(s):  
James B Boyd ◽  
Jack M Presley
Keyword(s):  
Drosophila Melanogaster ◽  
Uv Irradiation ◽  
Detectable Effect ◽  
X Rays ◽  
Repair Synthesis ◽  
X Ray ◽  
Post Irradiation ◽  
First Instar ◽  
Isopycnic Centrifugation

ABSTRACT Repair replication of DNA has been studied in first instar larvae of Drosophila melanogaster with isopycnic centrifugation techniques. Larvae were fed BUdR, FUdR, streptomycin, penicillin, and Fungazone for two to four hours prior to exposure to UV, X-rays, MMS, or EMS. Feeding was continued for four hours in the presence of 3HBUdR and DNA was isolated from whole larvae. Repair replication is stimulated by each of these agents. MMS is about 10 times as potent as EMS in stimulating repair synthesis. A dose of 200 ergs/mm2 largely saturates the level of repair replication observed after UV irradiation. Repair replication rises between 0 and 80,000 R of X-rays before falling off. Semiconservative synthesis is seriously inhibited above a dose of 40,000 R of X-rays. Photorepair has been detected as a reduction in repair synthesis resulting from post-irradiation exposure to photoreactivating light. The same treatment has no detectable effect on X-ray-stimulated repair replication. Repair replication is insensitive to the presence of caffeine or hydroxyurea during the final incubation, although semiconservative synthesis is strongly inhibited by these agents. A mixture of BUdR and 3HTdR can be used to replace 3HBUdR in detecting repair replication.

The effects of x-ray radiation on the eye development of zebrafish

2014 ◽  
Vol 33 (10) ◽  
pp. 1040-1050 ◽  
Author(s):  
R Zhou ◽  
J Si ◽  
H Zhang ◽  
Z Wang ◽  
J Li ◽  
...  
Keyword(s):  
Eye Development ◽  
Model Organism ◽  
Control Group ◽  
X Rays ◽  
Heterogeneous Distribution ◽  
X Ray ◽  
Radiation Induced ◽  
High Doses ◽  
Lens Formation ◽  
Nuclear Cell

The toxic effects of x-ray radiation on eye development was measured using zebrafish as a model organism. Zebrafish embryos at 8 h post-fertilization (hpf) were irradiated using X-rays at doses of 1, 2, 4, and 8 Gy. At 24 and 48 hpf, x-ray radiation induced a significant increase in reactive oxygen species (ROS) content and cell apoptotic signals. Both of these increases were dose dependent and there were significant positive relationships between them at 24 hpf. At 48 and 72 hpf, the increase of ROS concentration can be eliminated by increasing activities of superoxide dismutase and catalase. Although the ROS generated by x-ray radiation caused a significant increase in cell apoptosis at 24 and 48 hpf, the cellular layers of the retina and lens formation in the irradiated groups were not significantly disrupted at 144 hpf compared with the control group, with the exception of a heterogeneous distribution of the cells in inner nuclear cell layer and a significant decrease in the diameters of whole eyes after 8 Gy irradiation. X-Ray radiation at later stages of gastrulation may not cause distinct optic complications; however, there is still a risk of microophthalmia at high doses of irradiation.

scholarly journals THE EFFECT OF HIGH DOSES OF X-IRRADIATION ON THE PHAGOCYTIC, PROLIFERATIVE, AND METABOLIC PROPERTIES OF THE RETICULO-ENDOTHELIAL SYSTEM

1959 ◽  
Vol 110 (1) ◽  
pp. 49-64 ◽  
Author(s):  
B. Benacerraf ◽  
Evelyn Kivy-Rosenberg ◽  
Martha M. Sebestyen ◽  
Benjamin W. Zweifach
Keyword(s):  
Slow Rate ◽  
Colloidal Particles ◽  
X Rays ◽  
X Ray ◽  
E Coli ◽  
Denatured Protein ◽  
X Irradiation ◽  
Metabolic Properties ◽  
High Doses ◽  
Reticulo Endothelial System

The effect of moderately high doses of x-irradiation upon the reticulo-endothelial system of mice and rats was investigated. A dosage of 600 r to mice and 850 r to rats did not interfere with the ability of the RES to clear colloidal particles from the blood. However the 850 r x-ray dose to rats prevented recovery of normal phagocytic function after "blockade." In mice, 600 r interfered with the ability of the RES to respond to the usual stimulating effect of zymosan. The ability of the RES of mice which have received 600 r of x-rays to clear P32-labelled E. coli from the blood was not significantly altered. These mice responded poorly to immunization, as demonstrated by the slow rate of clearance of the bacteria from the blood of immunized, irradiated individuals as compared with that of immunized controls. This reflected the lowered antibody production and not deficiency of phagocytic mechanism. There was no evidence of a changed capacity of the Kupffer cells of mice which had received 600 r of x-rays to break down denatured protein enzymatically.

scholarly journals Differences in responses to X-ray exposure between osteoclast and osteoblast cells

2017 ◽  
Vol 58 (6) ◽  
pp. 791-802 ◽  
Author(s):  
Jian Zhang ◽  
Ziyang Wang ◽  
Anqing Wu ◽  
Jing Nie ◽  
Hailong Pei ◽  
...  
Keyword(s):  
Bone Resorption ◽  
Bone Loss ◽  
Osteoclast Differentiation ◽  
Inhibitory Effect ◽  
Health Concern ◽  
X Rays ◽  
Potential Health ◽  
X Ray ◽  
Radiation Induced ◽  
High Doses

Abstract Radiation-induced bone loss is a potential health concern for cancer patients undergoing radiotherapy. Enhanced bone resorption by osteoclasts and decreased bone formation by osteoblasts were thought to be the main reasons. In this study, we showed that both pre-differentiating and differentiating osteoclasts were relatively sensitive to X-rays compared with osteoblasts. X-rays decreased cell viability to a greater degree in RAW264.7 cells and in differentiating cells than than in osteoblastic MC3T3-E1 cells. X-rays at up to 8 Gy had little effects on osteoblast mineralization. In contrast, X-rays at 1 Gy induced enhanced osteoclastogenesis by enhanced cell fusion, but had no effects on bone resorption. A higher dose of X-rays at 8 Gy, however, had an inhibitory effect on bone resorption. In addition, actin ring formation was disrupted by 8 Gy of X-rays and reorganized into clusters. An increased activity of Caspase 3 was found after X-ray exposure. Actin disorganization and increased apoptosis may be the potential effects of X-rays at high doses, by inhibiting osteoclast differentiation. Taken together, our data indicate high radiosensitivity of osteoclasts. X-ray irradiation at relatively low doses can activate osteoclastogenesis, but not osteogenic differentiation. The radiosensitive osteoclasts are the potentially responsive cells for X-ray-induced bone loss.

scholarly journals An ensemble of new techniques to study soft-X-ray-induced variations in cellular metabolism

2004 ◽  
Vol 22 (3) ◽  
pp. 323-333 ◽  
Author(s):  
EDMOND TURCU ◽  
RICK ALLOT ◽  
NICOLA LISI ◽  
DIMITRI BATANI ◽  
FULVIA BORTOLOTTO ◽  
...  
Keyword(s):  
Laser Plasma ◽  
Metabolic Response ◽  
Cell Metabolism ◽  
Plasma Source ◽  
Yeast Cells ◽  
X Rays ◽  
New Techniques ◽  
X Ray ◽  
Cell Compartments ◽  
High Doses

An ensemble of new techniques has been developed to study cell metabolism. These include: CO2production monitoring, cell irradiation with soft X rays produced with a laser-plasma source, and study of oscillations in cell metabolic activity via spectral analysis of experimental records. Soft X-rays at about 0.9 keV, with a very low penetration in biological material, were chosen to produce damages at the metabolic level, without great interference with DNA activity. The use of a laser-plasma source allowed a fast deposition of high doses. Monitoring of CO2production allowed us to measure cell metabolic response immediately after irradiation in a continuous and noninvasive way. Also a simple model was developed to calculate X-ray doses delivered to the different cell compartments following a Lambert–Bouguet–Beer law. Results obtained onSaccharomyces cerevisiaeyeast cells in experiments performed at Rutherford Appleton Laboratory are presented.

White-Light Coronal Structures: Streamers and CMEs

1994 ◽  
Vol 144 ◽  
pp. 82
Author(s):  
E. Hildner
Keyword(s):  
Emission Line ◽  
Electron Density ◽  
White Light ◽  
Coronal Mass Ejections ◽  
X Rays ◽  
Solar Cycles ◽  
Temperature Function ◽  
X Ray ◽  
Eclipse Observations ◽  
Coronal Structures

AbstractOver the last twenty years, orbiting coronagraphs have vastly increased the amount of observational material for the whitelight corona. Spanning almost two solar cycles, and augmented by ground-based K-coronameter, emission-line, and eclipse observations, these data allow us to assess,inter alia: the typical and atypical behavior of the corona; how the corona evolves on time scales from minutes to a decade; and (in some respects) the relation between photospheric, coronal, and interplanetary features. This talk will review recent results on these three topics. A remark or two will attempt to relate the whitelight corona between 1.5 and 6 R⊙to the corona seen at lower altitudes in soft X-rays (e.g., with Yohkoh). The whitelight emission depends only on integrated electron density independent of temperature, whereas the soft X-ray emission depends upon the integral of electron density squared times a temperature function. The properties of coronal mass ejections (CMEs) will be reviewed briefly and their relationships to other solar and interplanetary phenomena will be noted.

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