scholarly journals Low Dose Ionizing Radiation Strongly Stimulates Insertional Mutagenesis in a γH2AX Dependent Manner

2019 ◽  
Author(s):  
Alex N. Zelensky ◽  
Mascha Schoonakker ◽  
Inger Brandsma ◽  
Marcel Tijsterman ◽  
Dik C. van Gent ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Insertional Mutagenesis ◽  
High Efficiency ◽  
Direct Detection ◽  
Radiation Risk ◽  
Dependent Manner ◽  
Sequence Specificity ◽  
Induced Mutations ◽  
Histone H2ax ◽  
Non Homologous End Joining

AbstractExtrachromosomal DNA can integrate into the genome with no sequence specificity producing an insertional mutation. This process, which is referred to as random integration (RI), requires a double stranded break (DSB) in the genome. Inducing DSBs by various means, including ionizing radiation, increases the frequency of integration. Here we report that non-lethal physiologically relevant doses of ionizing radiation (10-100 mGy), within the range produced by medical imaging equipment, stimulate RI of transfected and viral episomal DNA in human and mouse cells with an extremely high efficiency. Genetic analysis of stimulated RI (S-RI) revealed that it is distinct from the background RI, requires histone H2AX S139 phosphorylation (γH2AX) and is not reduced by DNA polymerase θ (Polq) inactivation. S-RI efficiency was unaffected by the main DSB repair pathway (homologous recombination and non-homologous end joining) disruptions, but double deficiency in MDC1 and 53BP1 phenocopies γH2AX inactivation. The robust responsiveness of S-RI to physiological amounts of DSBs has implications for radiation risk assessment and can be exploited for extremely sensitive, macroscopic and direct detection of DSB-induced mutations.

scholarly journals Low dose ionizing radiation strongly stimulates insertional mutagenesis in a γH2AX dependent manner

PLoS Genetics ◽  
2020 ◽  
Vol 16 (1) ◽  
pp. e1008550 ◽  
Author(s):  
Alex N. Zelensky ◽  
Mascha Schoonakker ◽  
Inger Brandsma ◽  
Marcel Tijsterman ◽  
Dik C. van Gent ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Insertional Mutagenesis ◽  
Low Dose ◽  
Dependent Manner

scholarly journals Rapid and high efficiency transformation of Chlamydomonas reinhardtii by square-wave electroporation

2019 ◽  
Vol 39 (1) ◽  
Author(s):  
Liang Wang ◽  
Lijing Yang ◽  
Xin Wen ◽  
Zhuoya Chen ◽  
Qiaoying Liang ◽  
...  
Keyword(s):  
Chlamydomonas Reinhardtii ◽  
Insertional Mutagenesis ◽  
Molecular Mechanisms ◽  
High Efficiency ◽  
Model Organism ◽  
Dependent Manner ◽  
Exogenous Dna ◽  
Square Wave ◽  
Physiological Processes ◽  
Final Yield

Abstract Chlamydomonas reinhardtii, the unicellular green algae, is the model organism for studies in various physiological processes and for bioindustrial applications. To explore the molecular mechanisms underlying physiological processes or to establish engineered cell lines, the exogenous DNA needs to be integrated into the genome for the insertional mutagenesis or transgene expression. However, the amount of selected marker DNA is not seriously considered in the existing electroporation methods for mutants library construction. Here, we reported a rapid-and-high-efficiency transformation technique for cell-walled strains using square-wave electroporation system. The final yield with this electroporation method was 2–6 × 103 transformants per μg exogenous DNA for cell-walled strains in a strain-dependent manner. In general, this electroporation technique was the easy and applicable way to build a mutant library for screening phenotypes of interest.

Radiopharmacology: Hazard or/and Benefit

1984 ◽  
Vol 23 (02) ◽  
pp. 87-91 ◽  
Author(s):  
K. Flemming
Keyword(s):  
Ionizing Radiation ◽  
Late Effects ◽  
Radiation Risk ◽  
Dose Effect ◽  
Radiation Hazard ◽  
Radiation Doses ◽  
Low Doses ◽  
Medical Radiology ◽  
Experimental Findings ◽  
In The Beginning

SummaryIn the beginning of medical radiology, only the benefit of ionizing radiation was obvious, and radiation was handled and applied generously. After late effects had become known, the radiation exposure was reduced to doses following which no such effects were found. Thus, it was assumed that one could obtain an optimal medical benefit without inducing any hazard. Later, due to experimental findings, hypotheses arose (linear dose-effect response, no time factor) which led to the opinion that even low and lowest radiation doses were relevant for the induction of late effects. A radiation fear grew, which was unintentionally strengthened by radiation protection decrees: even for low doses a radiation risk could be calculated. Therefore, it was believed that there could still exist a radiation hazard, and the radiation benefit remained in question. If, however, all presently known facts are considered, one must conclude that large radiation doses are hazardous and low doses are inefficient, whereas lowest doses have a biopositive effect. Ionizing radiation, therefore, may cause both, hazard as well as benefit. Which of the two effects prevails is determined by the level of dose.

Requesting physicians’ knowledge of X-radiation exposure from computed tomography scan examinations: A case study of two Nigerian tertiary hospitals

2020 ◽  
Vol 3 ◽  
pp. 36-39
Author(s):  
Samson O. Paulinus ◽  
Benjamin E. Udoh ◽  
Bassey E. Archibong ◽  
Akpama E. Egong ◽  
Akwa E. Erim ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Ionizing Radiation ◽  
Ct Scan ◽  
Radiation Exposure ◽  
Work Experience ◽  
Radiation Risk ◽  
Radiological Protection ◽  
X Ray ◽  
Tertiary Hospitals ◽  
Medical Exposure

Objective: Physicians who often request for computed tomography (CT) scan examinations are expected to have sound knowledge of radiation exposure (risks) to patients in line with the basic radiation protection principles according to the International Commission on Radiological Protection (ICRP), the Protection of Persons Undergoing Medical Exposure or Treatment (POPUMET), and the Ionizing Radiation (Medical Exposure) Regulations (IR(ME)R). The aim is to assess the level of requesting physicians’ knowledge of ionizing radiation from CT scan examinations in two Nigerian tertiary hospitals. Materials and Methods: An 18-item-based questionnaire was distributed to 141 practicing medical doctors, excluding radiologists with work experience from 0 to >16 years in two major teaching hospitals in Nigeria with a return rate of 69%, using a voluntary sampling technique. Results: The results showed that 25% of the respondents identified CT thorax, abdomen, and pelvis examination as having the highest radiation risk, while 22% said that it was a conventional chest X-ray. Furthermore, 14% concluded that CT head had the highest risk while 9% gave their answer to be conventional abdominal X-ray. In addition, 17% inferred that magnetic resonance imaging had the highest radiation risk while 11% had no idea. Furthermore, 25.5% of the respondents have had training on ionizing radiation from CT scan examinations while 74.5% had no training. Majority (90%) of the respondents were not aware of the ICRP guidelines for requesting investigations with very little (<3%) or no knowledge (0%) on the POPUMET and the IR(ME)R respectively. Conclusion: There is low level of knowledge of ionizing radiation from CT scan examinations among requesting physicians in the study locations.

scholarly journals Replication Stress-Associated DSBs Induced by Ionizing Radiation Risk Genomic Destabilization and Associated Clonal Evolution

iScience ◽  
2021 ◽  
pp. 102313
Author(s):  
Yusuke Matsuno ◽  
Mai Hyodo ◽  
Mafuka Suzuki ◽  
Yosuke Tanaka ◽  
Yasunori Horikoshi ◽  
...  
Keyword(s):  
Ionizing Radiation ◽  
Clonal Evolution ◽  
Radiation Risk ◽  
Replication Stress

scholarly journals An improved method for precise genome editing in zebrafish using CRISPR-Cas9 technique

2021 ◽  
Author(s):  
Eugene V. Gasanov ◽  
Justyna Jędrychowska ◽  
Michal Pastor ◽  
Malgorzata Wiweger ◽  
Axel Methner ◽  
...  
Keyword(s):  
Genome Editing ◽  
High Efficiency ◽  
Target Site ◽  
Proof Of Concept ◽  
Intervention Site ◽  
End Joining ◽  
Guide Rna ◽  
Guide Rnas ◽  
Cas9 Nuclease ◽  
Non Homologous End Joining

AbstractCurrent methods of CRISPR-Cas9-mediated site-specific mutagenesis create deletions and small insertions at the target site which are repaired by imprecise non-homologous end-joining. Targeting of the Cas9 nuclease relies on a short guide RNA (gRNA) corresponding to the genome sequence approximately at the intended site of intervention. We here propose an improved version of CRISPR-Cas9 genome editing that relies on two complementary guide RNAs instead of one. Two guide RNAs delimit the intervention site and allow the precise deletion of several nucleotides at the target site. As proof of concept, we generated heterozygous deletion mutants of the kcng4b, gdap1, and ghitm genes in the zebrafish Danio rerio using this method. A further analysis by high-resolution DNA melting demonstrated a high efficiency and a low background of unpredicted mutations. The use of two complementary gRNAs improves CRISPR-Cas9 specificity and allows the creation of predictable and precise mutations in the genome of D. rerio.

Uptake of taurocholic acid and cholic acid in isolated hepatocytes from rainbow trout

1994 ◽  
Vol 267 (3) ◽  
pp. G380-G386 ◽  
Author(s):  
C. M. Rabergh ◽  
K. Ziegler ◽  
B. Isomaa ◽  
M. M. Lipsky ◽  
J. E. Eriksson
Keyword(s):  
Rainbow Trout ◽  
Bile Acids ◽  
Low Temperatures ◽  
High Efficiency ◽  
Isolated Hepatocytes ◽  
Metabolic Inhibitors ◽  
Dependent Manner ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Transport Component ◽  
Efficient Uptake

The uptake of the bile acids cholate (CHA) and taurocholate (TCHA) was studied in isolated hepatocytes from rainbow trout (Oncorhynchus mykiss). Both CHA and TCHA were taken up in a concentration- and temperature-dependent manner with optimum temperature at 15 degrees C and a strikingly efficient uptake even at low temperatures (0-5 degrees C). The total uptake was a combination of a saturable [Michaelis-Menten constant (Km) for CHA, 20 microM; Km for TCHA, 19 microM] and a nonsaturable component. The maximal uptake rate of the saturable component was 416 and 805 pmol.mg protein-1.min-1 for CHA and TCHA, respectively. The uptake of both bile acids was shown to be energy dependent, since it was inhibited by the metabolic inhibitors antimycin A, oligomycin and carbonyl cyanide m-chlorophenylhydrazone. The uptake was clearly Na+ independent, since isosmotic replacement of extracellular Na+ by Li+, choline, or K+ did not inhibit the uptake. Furthermore, it seemed to be independent of the presence of extracellular Cl-, since it was not inhibited by replacement of Cl- with sodium gluconate. On the whole, our results show that the hepatocellular uptake of bile acids in rainbow trout is mediated by a Na(+)-independent carrier system, with characteristics resembling the corresponding transport component in mammalian hepatocytes, but with high efficiency even at low temperatures.

scholarly journals Multicomponent differentiation-regulated transcription factors in F9 embryonal carcinoma stem cells.

1991 ◽  
Vol 11 (3) ◽  
pp. 1686-1695 ◽  
Author(s):  
M K Shivji ◽  
N B La Thangue
Keyword(s):  
Stem Cells ◽  
Transcription Factors ◽  
Dna Binding ◽  
Embryonal Carcinoma ◽  
Regulatory Sequence ◽  
Dependent Manner ◽  
Sequence Specificity ◽  
Dna Sequence Specificity ◽  
Cell Extracts

Murine F9 embryonal carcinoma (F9 EC) stem cells have an E1a-like transcription activity that is down-regulated as these cells differentiate to parietal endoderm. For the adenovirus E2A promoter, this activity requires at least two sequence-specific transcription factors, one that binds the cyclic AMP-responsive element (CRE) and the other, DRTF1, the DNA-binding activity of which is down-regulated as F9 EC cells differentiate. Here we report the characterization of several binding activities in F9 EC cell extracts, referred to as DRTF 1a, 1b and 1c, that recognize the DRTF1 cis-regulatory sequence (-70 to -50 region). These activities can be chromatographically separated but are not distinguishable by DNA sequence specificity. Activity 1a is a detergent-sensitive complex in which DNA binding is regulated by phosphorylation. In contrast, activities 1b and 1c are unaffected by these treatments but exist as multicomponent protein complexes even before DNA binding. Two sets of DNA-binding polypeptides, p50DR and p30DR, affinity purified from F9 EC cell extracts produce complexes 1b and 1c. Both polypeptides appear to be present in the same DNA-bound protein complex and both directly contact DNA. These affinity-purified polypeptides activate transcription in vitro in a binding-site-dependent manner. These data indicate the in F9 EC stem cells, multicomponent differentiation-regulated transcription factors contribute to the cellular E1a-like activity.

scholarly journals Natural ionizing radiation and human health in Serbia

2010 ◽  
Vol 25 (3) ◽  
pp. 192-197 ◽  
Author(s):  
Danijela Obradovic-Arsic ◽  
Snezana Nenadovic ◽  
Dejan Filipovic ◽  
Bojana Mihajlovic
Keyword(s):  
General Population ◽  
Ionizing Radiation ◽  
Human Health ◽  
Health Effects ◽  
Population Health ◽  
Natural Radionuclides ◽  
Radiation Risk

This paper provides information about potential effects of natural ionizing radiation on general population health. Natural radionuclides are particularly stressed, as well as health effects of high and lower doses. Radio-ecological areals have been presented for Serbia, while radiation risk has been assessed for the population of Serbia according to census years.

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