Long term effects of Chernobyl contamination on DNA repair function and plant resistance to different biotic and abiotic stress factors

Thirty years after the Chernobyl explosion we still lack information regarding the genetic effects of radionuclide contamination on the plant population. For example, are plants adapting to the low dose of chronic ionising irradiation and showing improved resistance to radiation damage? Are they coping with changing/increased pathogenicity of fungi and viruses in the Chernobyl exclusion (ChE) zone? Are plant populations rapidly accumulating mutational load and should we expect rapid micro-evolutionary changes in plants in the Chernobyl area? This review will try to summarise the current knowledge on these aspects of plant genetics and ecology and draw conclusions on the importance of further studies in the area around Chernobyl.     

Uptake of Gallium-67 in Colonic and Rectal Tumours

The uptake of ⁶⁷Ga in biopsy specimens of normal and abnormal tissue was measured in 20 cases of colonic and rectal disease and the ratio between the ⁶⁷Ga uptake in these diseases and in the normal colon or rectum was determined. Uptake of the isotope was high in most of the 14 primary malignant tumours, being highest in poorly differentiated tumours. This uptake was found to be concentrated at the active tumour edge. Uptake of the isotope was generally low in non-malignant lesions.     

Altered biodistribution of indium-111-labeled monoclonal antibody 96.5 to tumors and normal tissues of nude mice bearing human melanoma xenografts in visceral organs

Summary Human melanoma xenografts were produced in the subcutis, kidney, cecum and liver of different nude mice. An¹¹¹In-labeled anti-(human melanoma) monoclonal antibody (96.5) or an¹¹¹In-labeled nonspecific control monoclonal antibody (ZCE-025) was injected intravenously in separate groups of mice. Radioactive antibody accumulation was measured in tumor, blood, viscera, and carcasses. mAb 96.5 targeted specifically to tumor tissue regardless of site of growth. Tumors in the liver exhibited significantly (P <0.05) higher tumor-to-blood ratios (45±6, mean ±SEM) than xenografts at other visceral organs, the lowest value being found for subcutaneous melanoma (2.6±0.5). The differences in tumor-to-blood ratio were due to significant alterations of antibody biodistribution, since the actual antibody concentration in the different tumor sites was similar. The percentage of recovered anti-melanoma antibody per milliliter of blood in mice with visceral lesions (4.6±1.1%/ml) was significantly lower than that found in mice with subcutaneous tumors (9.5±1.4%/ml,P <0.05). Moreover, significantly higher levels (18.2±3.2%/g, 31.0±5.1%/g, respectively) of the melanoma mAb 96.5 were found in normal liver and spleen tissue recovered from mice with visceral tumors as compared to tissue from mice with subcutaneous tumors (9.2±0.9%/g, 13.5±1.9%/g, respectively;P <0.05). These results demonstrate that the presence of visceral tumor can significantly affect tumor-to-blood ratios, blood levels, and biodistribution of¹¹¹In-labeled mAb 96.5.This work was supported in part by funds from the National Institutes of Health, National Cancer Institute, Grant R35-CA42107 and Core Grant CA16672     

Reduction of Selenate and Selenite to Elemental Selenium by a Pseudomonas stutzeri Isolate

A Pseudomonas stutzeri isolate rapidly reduced both selenite and selenate ions to elemental selenium at initial concentrations of both anions of up to 48.1 mM. Optimal selenium reduction occurred under aerobic conditions between pH 7.0 and 9.0 and at temperatures of 25 to 35°C. Reduction of both selenite and selenate was unaffected by a number of anions except for sulfite, chromate, and tungstate ions, which inhibited both growth and reduction.     

Recombination associated with replication of malarial mitochondrial DNA.

Mitochondrial DNA of the malarial parasite Plasmodium falciparum comprises approximately 20 copies per cell of a 6 kb genome, arranged mainly as polydisperse linear concatemers. In synchronous blood cultures, initiation of mtDNA replication coincides with the start of the 4-5 doublings in nuclear DNA that mark the reproductive phase of the erythrocytic cycle. We show that mtDNA replication coincides with a recombination process reminiscent of the replication mechanism used by certain bacteriophages and plasmids. The few circular forms of mtDNA which are also present do not replicate by a theta mechanism, but are themselves the product of recombination, and we propose they undergo rolling circle activity to generate the linear concatemers.     

Fission yeast rad17: a homologue of budding yeast RAD24 that shares regions of sequence similarity with DNA polymerase accessory proteins.

Following DNA damage or a block to DNA synthesis, checkpoint pathways act to arrest mitosis and prevent the attempted segregation of damaged or unreplicated DNA. The rad17 locus of Schizosaccharomyces pombe is one of seven known radiation-sensitive (rad) loci which are absolutely required to prevent mitosis following DNA damage in fission yeast. Six of these (rad1, rad3, rad9, rad17, rad26 and hus1) are also required for the checkpoint which prevents mitosis from occurring before DNA replication is complete. We report here that the predicted rad17 gene product is a basic hydrophilic protein of 606 amino acids which contains five domains with sequence homology to replication factor C (RF-C)/activator 1 subunits. Western analysis and fusion with Green Fluorescent Protein indicate that the abundance and electrophoretic mobility of Rad17 is not significantly modified following a block to DNA synthesis or following DNA damage, and that Rad17 is localized in the nucleus. Rad17 function is not essential for growth, but is required for the function of the DNA structure-dependent checkpoints. Site-directed mutagenesis has been used to demonstrate the biological significance of the RF-C/activator 1-related domains. These studies have also defined an element of the radiation sensitivity caused by loss of Rad17 function which is not associated with the radiation-induced G2 arrest defect seen in the rad17.d null mutant cells.     

A comparison of small circular DNA molecules in psi+ and psi- strains of Saccharomyces cerevisiae.

The psi+ and psi- phenotypes, which affect the efficiency of ochre suppression in yeast, are inherited in a non-Mendelian fashion. There is no apparent difference in length or in length distribution of 2 micronm circular DNA molecules between psi+ and psi- strains. It seems that the psi genetic determinant is probably not connected with the presence or absence of these small circular DNA molecules.     

Value of gallium scanning in seminoma of the testis.

Whole-body scanning using gallium-67-citrate gave consistently accurate tumour localisation in patients with seminoma of the testis. Thirteen out of 15 scans performed in patients with disseminated seminoma in relapse gave good imaging in all disease areas. Scans in patients with teratoma of the testis were less consistently positive; of nine scans performed in patients with disseminated teratoma seven were entirely negative and two scans lightly imaged large disease masses in two patients. In eight patients with combined (seminoma and teratoma) tumours the scan seemed to reflect the dominant tumour type at the time of scanning. In one of these patients the scans changed from positive to negative, being positive when seminoma was the dominant tumour and negative when a teratoma developed. Gallium-67-citrate scanning is useful in managing seminoma of the testis, both for determining the extent of disease present at initial presentation and for routine follow-up. It may be useful in the differential diagnosis of combined tumours when tumour masses are greater than 2 cm in diameter.     

Potential Sequential Exposures to 2-Butoxyethanol After Use of a Hard-Surface Cleaner

Professional workers and consumers frequently use hard-surface cleaning products and these products may contain glycol ethers (GEs), such as 2-Butoxyethanol (2-BE). Governmental agencies have set exposure limits for some chemicals used in cleaning products and these exposure limits have been used as guides to protect human health. The study objectives were to determine realistic inhalation exposures for professional workers performing multiple, sequential cleaning tasks and compare the exposures to the acute reference exposure level (REL), which California established for 2-BE. The ConsExpo model was acceptable for evaluating exposure based on a comparison of its predictions to experimentally measured 2-BE vapor concentrations from hard-surface cleaning. The typical worker exposure was predicted for a cleaning scenario consisting of three bathrooms and three kitchens (or three bedrooms) in a 1-h period. This exposure scenario would not be expected to result in significant health consequences because the predicted exposure was much lower than the REL. The predicted chronic and aggregate exposures were also acceptable. This analysis identified two important variables that affect inhalation exposure: cleaners should be used with adequate ventilation and wet wiping towels should be properly disposed so that they are not a source of continuing exposure.     

Keratinocyte galvanotaxis in combined DC and AC electric fields supports an electromechanical transduction sensing mechanism

Sedentary keratinocytes at the edge of a skin wound migrate into the wound, guided by the generation of an endogenous electric field (EF) generated by the collapse of the transepithelial potential. The center of the wound quickly becomes more negative than the surrounding tissue and remains the cathode of the endogenous EF until the wound is completely re‐epithelialized. This endogenous guidance cue can be studied in vitro. When placed in a direct current (DC) EF of physiological strength, 100 V/m, keratinocytes migrate directionally toward the cathode in a process known as galvanotaxis. Although a number of membrane‐bound (e.g., epidermal growth factor receptor (EGFR), integrins) and cytosolic proteins (cAMP, ERK, PI3K) are known to play a role in the downstream signaling mechanisms underpinning galvanotaxis, the initial sensing mechanism for this response is not understood. To investigate the EF sensor, we studied the migration of keratinocytes in a DC EF of 100 V/m, alternating current (AC) EFs of 40 V/m at either 1.6 or 160 Hz, and combinations of DC and AC EFs. In the AC EFs alone, keratinocytes migrated randomly. The 1.6 Hz AC EF combined with the DC EF suppressed the direction of migration but had no effect on speed. In contrast, the 160 Hz AC EF combined with the DC EF did not affect the direction of migration but increased the migration speed compared to the DC EF alone. These results can be understood in terms of an electromechanical transduction model, but not an electrodiffusion/osmosis or a voltage‐gated channel model. Bioelectromagnetics 34:85–94, 2013. © 2012 Wiley Periodicals, Inc.