A novel N-hydroxy-N′-aminoguanidine derivative inhibits ribonucleotide reductase activity: Effects in human HL-60 promyelocytic leukemia cells and synergism with arabinofuranosylcytosine (Ara-C)

Ribonucleotide reductase (RR; EC 1.17.4.1) is responsible for the de novo conversion of ribonucleoside diphosphates into deoxyribonucleoside diphosphates, which are essential for DNA replication. RR is upregulated in tumor cells and therefore considered to be an excellent target for cancer chemotherapy.ABNM-13 (N-hydroxy-2-(anthracene-2-yl-methylene)-hydrazinecarboximidamide), a novel N-hydroxy-N′-aminoguanidine has been designed to inhibit RR activity using 3D molecular space modeling techniques. In this study, we evaluated its effect on human HL-60 promyelocytic leukemia cells. ABNM-13 proved to be a potent inhibitor of RR which was displayed by significant alterations of deoxyribonucleoside triphosphate (dNTP) pool balance and a highly significant decrease of incorporation of radiolabeled cytidine into DNA of HL-60 cells. Diminished RR activity caused replication stress which was consistent with activation of Chk1 and Chk2, resulting in downregulation/degradation of Cdc25A. In contrast, Cdc25B was upregulated, leading to dephosphorylation and activation of Cdk1. The combined disregulation of Cdc25A and Cdc25B was the most likely cause for ABNM-13 induced S-phase arrest. Finally, we combined ABNM-13 with the first-line antileukemic agent arabinofuranosylcytosine (Ara-C) and found that ABNM-13 synergistically potentiated the antineoplastic effects of Ara-C.Due to these promising results, ABNM-13 deserves further preclinical and in vivo testing.     

Concentration gradients in evaporating binary droplets probed by spatially resolved Raman and NMR spectroscopy

Understanding the evaporation process of binary sessile droplets is essential for optimizing various technical processes, such as inkjet printing or heat transfer. Liquid mixtures whose evaporation and wetting properties may differ significantly from those of pure liquids are particularly interesting. Concentration gradients may occur in these binary droplets. The challenge is to measure concentration gradients without affecting the evaporation process. Here, spectroscopic methods with spatial resolution can discriminate between the components of a liquid mixture. We show that confocal Raman microscopy and spatially resolved NMR spectroscopy can be used as complementary methods to measure concentration gradients in evaporating 1-butanol/1-hexanol droplets on a hydrophobic surface. Deuterating one of the liquids allows analysis of the local composition through the comparison of the intensities of the C–H and C–D stretching bands in Raman spectra. Thus, a concentration gradient in the evaporating droplet was established. Spatially resolved NMR spectroscopy revealed the composition at different positions of a droplet evaporating in the NMR tube, an environment in which air exchange is less pronounced. While not being perfectly comparable, both methods—confocal Raman and spatially resolved NMR experiments—show the presence of a vertical concentration gradient as 1-butanol/1-hexanol droplets evaporate.

Evaporating droplets occur in various contexts such as inkjet printing (1, 2), heat transfer, or daily phenomena such as drying coffee stains (3, 4). In many applications, such as painting (5), cleaning, gluing, or printing (6), where liquid mixtures are used, the evaporation of a droplet is a complex process because the concentration profile within the droplet varies over time. To improve the controllability and predictability of the technical processes, it is essential to characterize the transport phenomena during the drying process. The measurement of the droplet composition is a crucial element and has to be carried out with sufficient spatial and temporal resolution. In particular, spectroscopic methods are promising tools for contactless concentration measurements of liquid mixtures.The evaporation of a droplet is governed by physical properties such as surface tension (7), density (8–10), vapor pressure (11), and boiling temperature. Additionally, concentration gradients can evolve in liquid mixtures (12). These gradients are driven by thermal gradients due to the enthalpy of evaporation (droplet cooling) or on heated surfaces, by surface tension gradients induced by preferential evaporation of one component or by density gradients for droplets composed of liquids with different densities like water and glycerol (13). The evaporation rates of the components can vary over the droplet surface. For sessile droplets with contact angles smaller than 90°, for example, the evaporation rates are higher at the three-phase contact line (14). These thermal or surface tension gradients can induce flow inside the droplet called Marangoni flow. This flow leads to concentration gradients across the droplet (7–10). The direction of the gradient depends on the density and surface tension. A direct application of this principle is, for instance, Marangoni cleaning in semiconductor technology (15).The investigation of the composition of sessile drops on the microliter scale, as they occur in inkjet printing or other technical processes, poses a challenge because the typical length scales of interest are smaller than the capillary length. In bulk samples, the composition can be examined in a straightforward manner with chromatographic methods such as gas chromatography and high-performance liquid chromatography or spectroscopic methods such as NMR spectroscopy, infrared spectroscopy, and Raman spectroscopy. However, for the investigation of sessile droplets, a high spatial and temporal resolution is required. For this purpose, confocal Raman spectroscopy and spatially resolved NMR spectroscopy are powerful tools. For both techniques, concentration determination is straightforward if at least two signals of the components of interest are baseline-separated. NMR is intrinsically calibration-free, whereas Raman spectroscopy requires calibration through reference experiments (16–18). Both approaches allow the quantification of concentration gradients in sessile droplets, as is shown here.In Raman microscopy, good spatial resolution can be achieved in a confocal setup. The components of mixtures can be distinguished via specific vibrations for different functional groups or through a careful analysis of the Raman signals in the fingerprint region (<1,500 cm⁻¹). For example, binary mixtures of ethanol and water can be characterized in a straightforward manner (17). If, however, both liquids have a similar chemical structure, the discrimination of the components might be hampered by signal overlap in the C–H stretching region (2,800 to 3,000 cm⁻¹); e.g., in such cases, Raman signals in the fingerprint region (<1,500 cm⁻¹) might be used for the identification of the species. However, these signals often provide a poor signal-to-noise ratio, which makes large integration times necessary. Thus, the image rate or resolution is so low that even slow diffusion processes are hardly resolved. Here, Raman stable isotope probing (SIP), which has been developed to monitor metabolic processes in microbiology, offers a solution (19). The basic idea of Raman SIP is to replace the proton in the C–H with deuterium in one of the mixture components such that the C–D stretching region occurs at roughly 1/2 times the C–H stretching and falls into a region with very weak or even without signals from the protonated liquid component. Thus, the concentration in a binary mixture can be calculated in a straightforward manner from the ratio of the integrated Raman intensities ICD/ICH of the respective stretching vibrations.Compared to Raman microscopy, where localization is achieved by scanning the focal point across the region of interest, in NMR experiments localization is achieved by using magnetic field gradients. Usually, one avoids phase boundaries (especially liquid–gas interfaces) in NMR experiments because they disturb the magnetic field homogeneity and reduce the spectral quality in terms of line shape and baseline separation of the resonances. Nevertheless, it has been shown that MRI can be used to characterize freezing water droplets (20), the infiltration of water into asphalts (21), and the evaporation of sessile droplets from porous surfaces (22–24). Additionally, NMR can be used to quantify the composition of binary droplets during evaporation (25).Thus, the use of both complementary approaches to characterize evaporating binary droplets may be beneficial. In this article, we discuss the capabilities of Raman SIP and NMR techniques to analyze the evolution of the composition of an evaporating sessile binary droplet. As a model system, a binary mixture of 1-butanol and 1-hexanol was used. This mixture shows a low volatility such that the evaporation process can be captured with both Raman and NMR spectroscopies. With Raman spectroscopy, it was possible to observe concentration gradients of 1-butan-d₉-ol over the height of the droplet during evaporation. NMR techniques were examined in terms of the capability to observe the evaporation of 1-butanol and yield time-dependent droplet composition with spatially resolved ¹H-NMR spectra. Furthermore, the contours of the evaporating droplets were tracked by optical measurements to characterize the time-dependent changes in the droplet dimensions. Flows induced by the concentration gradients were confirmed by astigmatic particle tracking velocimetry.     

Irreversible Electroporation of a Hepatocellular Carcinoma Lesion Adjacent to a Transjugular Intrahepatic Portosystemic Shunt Stent Graft

We report in a 65-year-old man hepatocellular carcinoma adjacent to a transjugular intrahepatic portosystemic shunt stent-graft which was successfully treated with irreversible electroporation (IRE). IRE is a new non-thermal tissue ablation technique which uses electrical pulses to induce cell necrosis by irreversible membrane poration. IRE proved to be more advantageous in the ablation of perivascular tumor with little injury to the surrounding structures.     

A dual echo approach to removing motion artefacts in fMRI time series

In fMRI, subject motion can severely affect data quality. This is a particular problem when movement is correlated with the experimental paradigm as this potentially causes artefactual activation. A method is presented that uses linear regression, to utilise the time course of an image acquired at very short echo time (TE) as a voxel‐wise regressor for a second image in the same echo train, that is acquired with high BOLD sensitivity. The value of this approach is demonstrated using task‐locked motion combined with visual stimulation. Results obtained at both 1.5 and 3 T show improvements in functional activation maps for individual subjects. The method is straightforward to implement, does not require extra scan time and can easily be embedded in a multi‐echo acquisition framework. Copyright © 2009 John Wiley & Sons, Ltd.     

A new method for determination of varicella-zoster virus immunoglobulin G avidity in serum and cerebrospinal fluid

Background  

Avidity determination of antigen-specific immunoglobulin G (IgG) antibodies is an established serological method to differentiate acute from past infections. In order to compare the avidity of varicella-zoster virus (VZV) IgG in pairs of serum and cerebrospinal fluid (CSF) samples, we developed a new technique of avidity testing, the results of which are not influenced by the concentration of specific IgG.     

Type A dissection following endovascular thoracic aortic stent-graft repair.

PURPOSE: To describe our experience with endovascular stent-graft repairs in the thoracic aorta focusing on the secondary complication of type A dissection. METHODS: Between January 1996 and April 2004, 73 patients were treated for traumatic thoracic aortic rupture (n=15), type B dissection (n=22), or atherosclerotic descending thoracic aortic aneurysms (TAA, n=36). A retrospective review of the records found 5 (6.8%) patients (3 men; median age 64 years, range 43-87) who experienced a type A dissection at a median 20 days (range 2-124) after thoracic stent-graft repair for 3 type B dissections, 1 TAA, and a late type I endoleak that appeared 28 months after initial stent-graft repair of a traumatic dissection. RESULTS: In 3 patients (2 dissections, 1 endoleak), a tear in the aortic wall at the proximal stent-graft was responsible for a retrograde type A dissection. Underlying disease was the cause of the type A dissection in the 2 other patients (1 dissection, 1 TAA) and was unrelated to the stent-grafts. Three patients underwent open surgery at 3, 26, and 124 days after stent-graft placement; 2 procedures were successful, but the third patient died 3 months later due to multiorgan failure. Two type A dissections were untreated: one patient died from cardiac tamponade 14 days after successful stent-graft exclusion of the type I endoleak; the other patient refused further treatment and survived. The procedure-related mortality following acute retrograde type A dissection was 40%. CONCLUSIONS: Endovascular stent-graft repair of the thoracic aorta is associated with lower morbidity and mortality rates than surgical repair, although potentially lethal complications, acute or delayed, may occur.     

Frequency of collateral blood flow in the infarct-related coronary artery in rupture of the ventricular septum after acute myocardial infarction

Patients with postinfarction ventricular septal rupture have poor residual or collateral blood flow in the infarct artery and do not benefit from ischemic preconditioning. This suggests that rupture of the ventricular septum occurs on an unprotected and unprepared myocardium.