In vivo evidence for translesion synthesis by the replicative DNA polymerase δ

The intolerance of DNA polymerase δ (Polδ) to incorrect base pairing contributes to its extremely high accuracy during replication, but is believed to inhibit translesion synthesis (TLS). However, chicken DT40 cells lacking the POLD3 subunit of Polδ are deficient in TLS. Previous genetic and biochemical analysis showed that POLD3 may promote lesion bypass by Polδ itself independently of the translesion polymerase Polζ of which POLD3 is also a subunit. To test this hypothesis, we have inactivated Polδ proofreading in pold3 cells. This significantly restored TLS in pold3 mutants, enhancing dA incorporation opposite abasic sites. Purified proofreading-deficient human Polδ holoenzyme performs TLS of abasic sites in vitro much more efficiently than the wild type enzyme, with over 90% of TLS events resulting in dA incorporation. Furthermore, proofreading deficiency enhances the capability of Polδ to continue DNA synthesis over UV lesions both in vivo and in vitro. These data support Polδ contributing to TLS in vivo and suggest that the mutagenesis resulting from loss of Polδ proofreading activity may in part be explained by enhanced lesion bypass.     

Association between high voltage overhead transmission lines and mental health: a cross-sectional study

We examined the association between residential proximity to 60 Hz high voltage (22-500 kV) overhead transmission lines (HVOTLs) and mental health (MH). The subjects were 223 mothers with a mean age of 37 years. The distance from the subject's residence to the closest HVOTL was measured on a map. MH status was assessed by the SF-36 Health Survey, which was scored on a 0-100 point scale, and an individual with a score of 52 points or less was defined as having poor MH. Logistic regression models were used to examine the association between the distance from the subjects' residence to the closest HVOTL and MH status. The prevalence of poor MH was 15%. Among the 223 subjects, 10 lived within 100 m of a HVOTL. The adjusted odds ratios (OR) for poor MH among those who lived 101-300 m or within 100 m from HVOTL were 1.29 (95% confidence interval (CI): 0.35-10.13) and 1.87 (95% CI: 0.35-10.13), respectively, against the reference category (300+ m). MH status was not significantly associated with the distance between the subject's residence and the closest HVOTL.     

EGFR T790M Mutation as a Possible Target for Immunotherapy; Identification of HLA-A*0201-Restricted T Cell Epitopes Derived from the EGFR T790M Mutation

Treatment with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), such as gefitinib and erlotinib, has achieved high clinical response rates in patients with non–small cell lung cancers (NSCLCs). However, over time, most tumors develop acquired resistance to EGFR-TKIs, which is associated with the secondary EGFR T790M resistance mutation in about half the cases. Currently there are no effective treatment options for patients with this resistance mutation. Here we identified two novel HLA-A*0201 (A2)-restricted T cell epitopes containing the mutated methionine residue of the EGFR T790M mutation, T790M-5 (MQLMPFGCLL) and T790M-7 (LIMQLMPFGCL), as potential targets for EGFR-TKI-resistant patients. When peripheral blood cells were repeatedly stimulated in vitro with these two peptides and assessed by antigen-specific IFN-γ secretion, T cell lines responsive to T790M-5 and T790M-7 were established in 5 of 6 (83%) and 3 of 6 (50%) healthy donors, respectively. Additionally, the T790M-5- and T790M-7-specific T cell lines displayed an MHC class I-restricted reactivity against NSCLC cell lines expressing both HLA-A2 and the T790M mutation. Interestingly, the NSCLC patients with antigen-specific T cell responses to these epitopes showed a significantly less frequency of EGFR-T790M mutation than those without them [1 of 7 (14%) vs 9 of 15 (60%); chi-squared test, p  =  0.0449], indicating the negative correlation between the immune responses to the EGFR-T790M-derived epitopes and the presence of EGFR-T790M mutation in NSCLC patients. This finding could possibly be explained by the hypothesis that immune responses to the mutated neo-antigens derived from T790M might prevent the emergence of tumor cell variants with the T790M resistance mutation in NSCLC patients during EGFR-TKI treatment. Together, our results suggest that the identified T cell epitopes might provide a novel immunotherapeutic approach for prevention and/or treatment of EGFR-TKI resistance with the secondary EGFR T790M resistance mutation in NSCLC patients.     

Moderate alcohol consumption is associated with better endothelial function: a cross sectional study

Background

Natural heterologous valved conduits with a diameter greater than 22 mm that can be used for right ventricular outflow tract reconstruction in adults are not commercially available. The purpose of this study was to measure by ultrasonography the maximum diameter of the distended jugular veins of horses and cattle, respectively, to identify a population of animals that would be suitable for post-mortem collection of jugular veins at sizes greater than 22 mm.

Methods

The study population included 60 Warmblood horses, 25 Freiberger horses, 20 Brown Swiss cows, and 20 Holstein cows (including 10 Holstein and 10 Red Holstein). The maximum cross-sectional diameter of the distended jugular veins was measured at a location half-way between the mandibular angle and the thoracic inlet. The thoracic circumference (heart girth length) was used as a surrogate of body size. The jugular vein diameters of the different populations were compared by analysis of variance and the association between heart girth length and jugular vein diameter was determined in each of the four study populations by linear regression analysis.

Results

There was considerable individual variation of jugular vein diameters within each of the four study populations. There was no statistically significant relationship between thoracic circumference and jugular vein diameter in any of the populations. The jugular vein diameters of Brown Swiss cows were significantly larger than those of any of the other populations. Warmblood horses had significantly larger jugular vein diameters compared to Freiberger horses.

Conclusion

The results of this study suggest that the production of bovine or equine xenografts with diameters of greater than 22 mm would be feasible. Differences between species and breeds need to be considered. However, prediction of the jugular vein diameter based on breed and heart girth length in an individual animal is inaccurate.     

Vertical Distribution and Estimated Doses from Artificial Radionuclides in Soil Samples around the Chernobyl Nuclear Power Plant and the Semipalatinsk Nuclear Testing Site

For the current on-site evaluation of the environmental contamination and contributory external exposure after the accident at the Chernobyl Nuclear Power Plant (CNPP) and the nuclear tests at the Semipalatinsk Nuclear Testing Site (SNTS), the concentrations of artificial radionuclides in soil samples from each area were analyzed by gamma spectrometry. Four artificial radionuclides (²⁴¹Am, ¹³⁴Cs, ¹³⁷Cs, and ⁶⁰Co) were detected in surface soil around CNPP, whereas seven artificial radionuclides (²⁴¹Am, ⁵⁷Co, ¹³⁷Cs, ⁹⁵Zr, ⁹⁵Nb, ⁵⁸Co, and ⁶⁰Co) were detected in surface soil around SNTS. Effective doses around CNPP were over the public dose limit of 1 mSv/y (International Commission on Radiological Protection, 1991). These levels in a contaminated area 12 km from Unit 4 were high, whereas levels in a decontaminated area 12 km from Unit 4 and another contaminated area 15 km from Unit 4 were comparatively low. On the other hand, the effective doses around SNTS were below the public dose limit. These findings suggest that the environmental contamination and effective doses on the ground definitely decrease with decontamination such as removing surface soil, although the effective doses of the sampling points around CNPP in the present study were all over the public dose limit. Thus, the remediation of soil as a countermeasure could be an extremely effective method not only for areas around CNPP and SNTS but also for areas around the Fukushima Dai-ichi Nuclear Power Plant (FNPP), and external exposure levels will be certainly reduced. Long-term follow-up of environmental monitoring around CNPP, SNTS, and FNPP, as well as evaluation of the health effects in the population residing around these areas, could contribute to radiation safety and reduce unnecessary exposure to the public.     

RAD18 and RAD54 cooperatively contribute to maintenance of genomic stability in vertebrate cells

Translesion DNA synthesis (TLS) and homologous DNA recombination (HR) are two major pathways that account for survival after post-replicational DNA damage. TLS functions by filling gaps on a daughter strand that remain after DNA replication caused by damage on the mother strand, while HR can repair gaps and breaks using the intact sister chromatid as a template. The RAD18 gene, which is conserved from lower eukaryotes to vertebrates, is essential for TLS in Saccharomyces cerevisiae. To investigate the role of RAD18, we disrupted RAD18 by gene targeting in the chicken B-lymphocyte line DT40. RAD18(-/-) cells are sensitive to various DNA-damaging agents including ultraviolet light and the cross-linking agent cisplatin, consistent with its role in TLS. Interestingly, elevated sister chromatid exchange, which reflects HR- mediated post-replicational repair, was observed in RAD18(-/-) cells during the cell cycle. Strikingly, double mutants of RAD18 and RAD54, a gene involved in HR, are synthetic lethal, although the single mutant in either gene can proliferate with nearly normal kinetics. These data suggest that RAD18 plays an essential role in maintaining chromosomal DNA in cooperation with the RAD54-dependent DNA repair pathway.     

A novel point mutation in congenital erythropoietic porphyria in two members of Japanese family

The molecular basis of the uroporphyrinogen III synthase (UROIIIS) deficiency was investigated in two members of a Japanese family. This defect in heme biosynthesis is responsible for a rare autosomal recessive disease: congenital erythropoietic porphyria (CEP) or Günther’s disease. The first patient was homoallelic for a novel missense mutation: a T to C transition of nucleotide 634 that predicted a serine to proline substitution at residue 212 (S212P). The second patient appeared heteroallelic, carrying the same missense mutation and a nonsense mutation: a C to T change at nucleotide 745, resulting in a premature stop at codon 249, instead of a glutamine (Q249X). The corresponding mutated proteins were expressed in Escherichia coli and no residual activity was observed. A family study was also performed to determine the carrier status. Received: 18 July 1995     

Contributions of various ions to the resting and action potentials of crayfish medial giant axons

Summary The membrane of crayfish medial giant axons is permeable at rest to ions in the rank K>Na>Ca>Cl. With K present, variation of the other ions has little or no effect, but with K absent the axon hyperpolarizes when Na is reduced or eliminated by replacement with Tris (slope ca. 30 mV/decade Na₀). The hyperpolarization is independent of the presence of Cl or its absence (substitution with methanesulfonate or isethionate). The resistance increases progressively as Na is removed. These changes persist after the spike is blocked with tetrodotoxin. An increase in Ca causes depolarization (slope ca. 20 mV/decade) provided K, Na and Cl are all absent, but in the presence of Cl there is little or no change in membrane potential on increasing Ca to 150mm. The depolarization induced by Ca is associated with an increased resistance. Spike electrogenesis involves Ca activation as well as Na activation, but the after-depolarization at the end of the spike is due to a conductance increase for Ca. Two alternative equivalent circuits for the resting and active membrane are discussed.     

CD271+ Subpopulation of Pancreatic Stellate Cells Correlates with Prognosis of Pancreatic Cancer and Is Regulated by Interaction with Cancer Cells

Pancreatic stellate cells (PSCs) play a crucial role in the aggressive behavior of pancreatic cancer. Although heterogeneity of PSCs has been identified, the functional differences remain unclear. We characterized CD271⁺ PSCs in human pancreatic cancer. Immunohistochemistry for CD271 was performed for 31 normal pancreatic tissues and 105 pancreatic ductal adenocarcinomas (PDACs). We performed flow cytometry and quantitative RT-PCR, and assessed CD271 expression in PSCs isolated from pancreatic tissues and the changes in CD271 expression in PSCs cocultured with cancer cells. We also investigated the pattern of CD271 expression in a SCID mouse xenograft model. In the immunohistochemical analyses, the CD271-high staining rates in pancreatic stroma in normal pancreatic tissues and PDACs were 2/31 (6.5%) and 29/105 (27.6%), respectively (p = 0.0069). In PDACs, CD271⁺ stromal cells were frequently observed on the edge rather than the center of the tumors. Stromal CD271 high expression was associated with a good prognosis (p = 0.0040). Flow cytometric analyses demonstrated CD271-positive rates in PSCs were 0–2.1%. Quantitative RT-PCR analyses revealed that CD271 mRNA expression was increased in PSCs after coculture with pancreatic cancer cells. However, the level of CD271 mRNA expression subsequently decreased after the transient increase. Furthermore, CD271 mRNA expression was decreased in PSCs migrating toward pancreatic cancer cells through Matrigel. In the xenograft model, CD271⁺ PSCs were present at tumor margins/periphery and were absent in the tumor core. In conclusion, CD271 was expressed in PSCs around pancreatic tumors, but not in the center of the tumors, and expression decreased after long coculture with pancreatic cancer cells or after movement toward pancreatic cancer cells. These findings suggest that CD271⁺ PSCs appear at the early stage of pancreatic carcinogenesis and that CD271 expression is significantly correlated with a better prognosis in patients with PDAC.