Depicting corrosion-born defects in pipelines with combined neutron/γ ray backscatter: a biomimetic approach

The identification of corrosion, cracks and defects in pipelines used for transporting oil and gas can reduce the possibility of leaks, and consequently, it can limit the extent of an environmental disaster, public hazard and the associated financial impact of such events. Typically, corrosion in oil pipelines is measured with non-destructive ultrasonic or electromagnetic techniques, on the basis that corrosion and defects are often manifest as a change of thickness in the steel from which pipelines are made. However, such approaches are not practical for underground pipelines and their deployment can be complicated for the case of pipelines covered by insulation. In this paper, we present an innovative, non-destructive testing technique, which exploits the backscatter of a combination of fast-neutron and γ radiation from steel samples of a variety of thicknesses consistent with changes that might arise due to corrosion of a pipe wall. Our research demonstrates the potential to measure and characterise different steel thicknesses by detecting both the elastic, fast-neutron backscatter and the Compton-scattered γ radiations, simultaneously. Further, we demonstrate that the presence of insulation yields a consistent and separable influence on the experimental, wall-thickness measurements. The data from experimental measurements are supported by a comprehensive Monte Carlo computer simulation study.

Parp1 localizes within the Dnmt1 promoter and protects its unmethylated state by its enzymatic activity

Background

Aberrant hypermethylation of CpG islands in housekeeping gene promoters and widespread genome hypomethylation are typical events occurring in cancer cells. The molecular mechanisms behind these cancer-related changes in DNA methylation patterns are not well understood. Two questions are particularly important: (i) how are CpG islands protected from methylation in normal cells, and how is this protection compromised in cancer cells, and (ii) how does the genome-wide demethylation in cancer cells occur. The latter question is especially intriguing since so far no DNA demethylase enzyme has been found.

Methodology/Principal Findings

Our data show that the absence of ADP-ribose polymers (PARs), caused by ectopic over-expression of poly(ADP-ribose) glycohydrolase (PARG) in L929 mouse fibroblast cells leads to aberrant methylation of the CpG island in the promoter of the Dnmt1 gene, which in turn shuts down its transcription. The transcriptional silencing of Dnmt1 may be responsible for the widespread passive hypomethylation of genomic DNA which we detect on the example of pericentromeric repeat sequences. Chromatin immunoprecipitation results show that in normal cells the Dnmt1 promoter is occupied by poly(ADP-ribosyl)ated Parp1, suggesting that PARylated Parp1 plays a role in protecting the promoter from methylation.

Conclusions/Significance

In conclusion, the genome methylation pattern following PARG over-expression mirrors the pattern characteristic of cancer cells, supporting our idea that the right balance between Parp/Parg activities maintains the DNA methylation patterns in normal cells. The finding that in normal cells Parp1 and ADP-ribose polymers localize on the Dnmt1 promoter raises the possibility that PARylated Parp1 marks those sequences in the genome that must remain unmethylated and protects them from methylation, thus playing a role in the epigenetic regulation of gene expression.

ERK1/2 phosphorylation is an independent predictor of complete remission in newly diagnosed adult acute lymphoblastic leukemia

Extracellular signal-regulated kinase-1/2 (ERK1/2) is frequently found constitutively activated (p-ERK1/2) in hematopoietic diseases, suggesting a role in leukemogenesis. The aim of this study was to assess the expression and clinical role of p-ERK1/2 in adult acute lymphoblastic leukemia (ALL). In 131 primary samples from adult de novo ALL patients enrolled in the Gruppo Italiano per le Malattie Ematologiche dell'Adulto (GIMEMA) Leucemia Acute Linfoide (LAL) 2000 protocol and evaluated by flow cytometry, constitutive ERK1/2 activation was found in 34.5% of cases; these results were significantly associated with higher white blood cell (WBC) values (P=.013). In a multivariate analysis, p-ERK1/2 expression was an independent predictor of complete remission achievement (P=.027). Effective approaches toward MEK inhibition need to be explored in order to evaluate whether this may represent a new therapeutic strategy for adult ALL patients.

The effect of an infusion of low molecular weight dextran on peripheral resistance in patients with arteriosclerosis

Low molecular weight dextran is frequently given to improve the flow of blood to the periphery, but its mode of action is uncertain. We measured the effect of an infusion of 500 ml of Dextran 40 on the peripheral resistance in 12 patients undergoing reconstructive surgery for atherosclerotic occlusion of the superficial femoral artery. After the infusion, values of packed cell volume and blood viscosity indicated haemodilution. There was a consistent increase in mean flow and a fall in peripheral resistance. There was no correlation between change in viscosity and change in peripheral resistance, but there was a good correlation between the percentage change in resistance and the initial resistance. This suggests that the increase in flow of blood was due to reflex vasodilatation rather than to any reduction in viscosity.

The hydraulic impedance of the lower limb: its relevance to the success of bypass operations for occlusion of the superficial femoral artery

Simultaneous measurements of pressure and flow waves were made in the course of 25 femoropopliteal bypass operations. From these measurements the the hydraulic impedance of the arterial system in the lower limb was calculated. The values obtained were correlated with the results of the operations. Although reconstruction reduced the impedance we were unable to predict accurately the probable result of the operation on the basis of these measurements. The results suggest that success is more closely related to a good collateral circulation than to "run off".

Undetected aorto-iliac insufficiency: a reason for early failure of saphenous vein bypass grafts for obstruction of the superficial femoral artery

A series of 29 femoropopliteal bypass operations is described. The patients were selected carefully to exclude those with clinical and aortographic evidence of aorto-iliac disease. A pulsatility index was calculated from the velocity waveforms recorded over the common femoral and popliteal arteries. The pulsatility index is the ratio of the amplitude of the waveform to its mean height over one cardiac cycle. There was a highly significant difference in the result of the operation between patients with a pulsatility index of 4 or more in the common femoral artery and patients with a pulsatility index of less than 4. We concluded that calculation of this pulsatility index provides useful additional evidence when selecting patients suitable for a femoropopliteal bypass.