Human immunodeficiency virus 1 (HIV-1)-specific reverse transcriptase (RT) inhibitors may suppress the replication of specific drug-resistant (E138K)RT HIV-1 mutants or select for highly resistant (Y181C-->C181I)RT HIV-1 mutants

Mutant HIV-1 that expresses a Glu138-->Lys substitution in its RT [(E138K)RT] is resistant to the HIV-1-specific RT inhibitor 2',5'-bis-O-(tert-butyldimethylsilyl)-3'-spiro-5"-(4"-amino-1",2"- oxathiole-2",2"-dioxide)pyrimidine (TSAO). However, cell cultures infected with this mutant were completely protected against virus-mediated destruction by micromolar concentrations of the HIV-1-specific RT inhibitors tetrahydroimidazo[4,5,1-jk][1,4]benzodiazepin-2(1H)-one and -thione (TIBO), nevirapine, and bis(heteroaryl)piperazine (BHAP). In contrast, cells infected with a virus mutant that expresses a Tyr181-->Cys substitution in its RT [(Y181C)RT] were not protected by nevirapine and TIBO and were only temporarily protected by BHAP. HIV-1 mutant that emerged under the latter conditions contained a Cys181-->Ile substitution in their RT [(LC181I)RT]. This mutant proved highly resistant to all HIV-1-specific RT inhibitors tested, except for several 1-(2-hydroxyethoxymethyl)-6-(phenylthio)thymine (HEPT) derivatives. When recombinant (C181I)RT was evaluated for susceptibility to the HIV-1-specific RT inhibitors, it was resistant to all inhibitors except the HEPT compounds. Since a (Y181F)RT HIV mutant strain was isolated from cells infected with (Y181C)RT HIV-1 and treated with BHAP, we postulate that the Ile codon was derived from a Cys-->Phe transversion mutation (TGT-->TTT), followed by a Phe-->Ile transversion mutation (TTT-->ATT).     

DCE-MRI of hepatocellular carcinoma: perfusion quantification with Tofts model versus shutter-speed model—initial experience

Objective

To quantify hepatocellular carcinoma (HCC) perfusion and flow with the fast exchange regime-allowed Shutter-Speed model (SSM) compared to the Tofts model (TM).

Materials and methods

In this prospective study, 25 patients with HCC underwent DCE-MRI. ROIs were placed in liver parenchyma, portal vein, aorta and HCC lesions. Signal intensities were analyzed employing dual-input TM and SSM models. ART (arterial fraction), K ^trans (contrast agent transfer rate constant from plasma to extravascular extracellular space), v _e (extravascular extracellular volume fraction), k _ep (contrast agent intravasation rate constant), and τ _i (mean intracellular water molecule lifetime) were compared between liver parenchyma and HCC, and ART, K ^trans, v _e and k _ep were compared between models using Wilcoxon tests and limits of agreement. Test–retest reproducibility was assessed in 10 patients.

Results

ART and v _e obtained with TM; ART, v _e , k _e and τ _i obtained with SSM were significantly different between liver parenchyma and HCC (p < 0.04). Parameters showed variable reproducibility (CV range 14.7–66.5 % for both models). Liver K ^trans and v _e ; HCC v _e and k _ep were significantly different when estimated with the two models (p < 0.03).

Conclusion

Our results show differences when computed between the TM and the SSM. However, these differences are smaller than parameter reproducibilities and may be of limited clinical significance.

     

A review of methods for solubility determination in biopharmaceutical drug characterization

Abstract

The significance of thermodynamic solubility in biopharmaceutical compound or drug characterization as well as the importance of having methods that accurately establish it have been extensively addressed. Nonetheless, its precise determination continues to remain a challenging task to accomplish. Even more so when the number of compounds to evaluate is high and the available amount of each compound is low, both of which are inevitable for the compound characterization during the drug development process. Except for the shake-flask method which is still considered as the ‘gold standard’ in obtaining thermodynamic data, it is currently difficult to say that another satisfactory model which is routinely used to determine thermodynamic solubility is being applied. Therefore, this review summarizes the various experimental approaches which are based on the classical shake flask method but have yet attempted to speed up the experimental process of obtaining such data more conveniently. The most important experimental features of these approaches are provided to the reader. Some advantages and disadvantages associated with each approach are also highlighted, consequently offering a resource to those looking for the most appropriate of the approaches that have already fared well at determining the biopharmaceutically relevant drug solubility.     

Acetylsalicylic Acid Reduces Passive Aortic Wall Stiffness and Cardiovascular Remodelling in a Mouse Model of Advanced Atherosclerosis

Acetylsalicylic acid (ASA) is widely used in secondary prevention of cardiovascular (CV) disease, mainly because of its antithrombotic effects. Here, we investigated whether ASA can prevent the progression of vessel wall remodelling, atherosclerosis, and CV complications in apolipoprotein E deficient (ApoE^−/−) mice, a model of stable atherosclerosis, and in ApoE^−/− mice with a mutation in the fibrillin-1 gene (Fbn1^C1039G+/−), which is a model of elastic fibre fragmentation, accompanied by exacerbated unstable atherosclerosis. Female ApoE^−/− and ApoE^−/−Fbn1^C1039G+/− mice were fed a Western diet (WD). At 10 weeks of WD, the mice were randomly divided into four groups, receiving either ASA 5 mg/kg/day in the drinking water (ApoE^−/− (n = 14), ApoE^−/−Fbn1^C1039G+/− (n = 19)) or plain drinking water (ApoE^−/− (n = 15), ApoE^−/−Fbn1^C1039G+/− (n = 21)) for 15 weeks. ApoE^−/−Fbn1^C1039G+/− mice showed an increased neutrophil–lymphocyte ratio (NLR) compared to ApoE^−/− mice, and this effect was normalised by ASA. In the proximal ascending aorta wall, ASA-treated ApoE^−/−Fbn1^C1039G+/− mice showed less p-SMAD2/3 positive nuclei, a lower collagen percentage and an increased elastin/collagen ratio, consistent with the values measured in ApoE^−/− mice. ASA did not affect plaque progression, incidence of myocardial infarction and survival of ApoE^−/−Fbn1^C1039G+/− mice, but systolic blood pressure, cardiac fibrosis and hypertrophy were reduced. In conclusion, ASA normalises the NLR, passive wall stiffness and cardiac remodelling in ApoE^−/−Fbn1^C1039G+/− mice to levels observed in ApoE^−/− mice, indicating additional therapeutic benefits of ASA beyond its classical use.     

Sliding mode based harmonic oscillator synchronization

This paper deals with the synchronization problem of harmonic oscillatory systems, such as two- and three-phase harmonic oscillators. Synchronization between referent and controlled harmonic oscillators, based on amplitude and phase control, is pursued by employing a variable structure control system. Synchronization is achieved by organizing sliding mode along the intersection of two appropriate nonlinear sliding surfaces, individually providing amplitude and phase identity. In case of three-phase harmonic oscillator synchronization an additional symmetry condition arises, which is handled by introduction of another sliding surface. Parameter perturbations and external disturbances are taken into consideration in control system design. Variable structure controllers for two- and three-phase synchronization are designed, which provide sliding mode along the intersection of sliding surfaces in finite time in spite of present disturbances. Ideal sliding dynamics is proved to be insensitive to internal and external disturbances resulting in an ideal harmonic response. Mathematical analysis as well as experimental and simulation results are presented.     

The PFKFB3 Inhibitor AZ67 Inhibits Angiogenesis Independently of Glycolysis Inhibition

Angiogenesis is the process of new blood vessel formation. In this complex orchestrated growth, many factors are included. Lately, focus has shifted to endothelial cell metabolism, particularly to the PFKFB3 protein, a key regulatory enzyme of the glycolytic pathway. A variety of inhibitors of this important target have been studied, and a plethora of biological effects related to the process of angiogenesis have been reported. However, recent studies have disputed their mechanism of action, questioning whether all the effects are indeed due to PFKFB3 inhibition. Remarkably, the most well-studied inhibitor, 3PO, does not bind to PFKFB3, raising questions about this target. In our study, we aimed to elucidate the effects of PFKFB3 inhibition in angiogenesis by using the small molecule AZ67. We used isothermal titration calorimetry and confirmed binding to PFKFB3. In vitro, AZ67 did not decrease lactate production in endothelial cells (ECs), nor ATP levels, but exhibited good inhibitory efficacy in the tube-formation assay. Surprisingly, this was independent of EC migratory and proliferative abilities, as this was not diminished upon treatment. Strikingly however, even the lowest dose of AZ67 demonstrated significant inhibition of angiogenesis in vivo. To our knowledge, this is the first study to demonstrate that the process of angiogenesis can be disrupted by targeting PFKFB3 independently of glycolysis inhibition.     

An implementation of the stiffness derivative method as a discrete analytical sensitivity analysis and its application to mixed mode in LEFM

In this work, an improvement in the stiffness derivative method based on a shape design sensitivity analysis is proposed, so that the error inherent in the finite difference procedure is avoided. For a global estimation of G from a given finite element solution, this approach is shown to be equivalent to the well-known J-integral when the latter is numerically implemented through its equivalent domain integral. However, it is verified that its direct application to 2D mixed mode problems of linear elastic fracture mechanics through the field decomposition technique yields estimates for G_I and G_II which are in general more accurate for the proposed method. The importance of the velocity field is also remarked and some suggestions for its choice are given.     

Discrete time sliding mode approach to synchronization of modulated two-phase harmonic oscillator

This paper explores two-phase harmonic oscillator synchronization with a referent oscillator, whose amplitude and phase are modulated by two arbitrary smooth functions, respectively. Synchronization between modulated referent and controlled oscillator is based on amplitude and phase control, and pursued by employing a discrete time variable structure control system. Synchronization is achieved by organizing a quasi-sliding mode along intersection of two appropriate nonlinear sliding surfaces. Discrete-time variable structure controllers are proposed, which provides the desired motion. Mathematical analysis as well as experimental results are presented.     

Sliding Manifold Design for Higher-order Sliding Mode Control of Linear Systems

International Journal of Control, Automation and Systems - The paper considers sliding manifold design for higher-order sliding mode (HOSM) in linear systems. In this case, the sliding manifold...