Rate-dependent and antiarrhythmic reentrant tachycardia (AVNRT) effects of simvastatin in isolated rabbit atrioventricular nodal model

Background and purpose: Several previous studies have shown the direct and indirect effects of statins on supraventricular and ventricular arrhythmia. The purpose of the present study is to determine (1) whether Simvastatin modifies the rate-dependent properties of the AV node, (2) to what extent such changes are related to effect of Simvastatin on the basic properties of AV nodal conduction and refractoriness. Materials and methods: AV nodal refractoriness (AVERP & AVFRP) and rate dependency protocols Fatigue and Facilitation were used to assesse the electrophysiological properties of AV node. We used an isolated perfussed rabbit with AV nodal preparation in one group (N=8). The stimulation protocols were carried out during control phase and in the presence of various concentrations of Simvastatin (0.5 , 0.8 , 1, 3 ,10 μm). Results: Simvastatin in concentration-dependent manner successfully prolonged effective and functional nodal refractory period (AVERP & AVFRP). Also an increase in Wenckebach cycle length was observed. Simvastatin in high concentration (3,10 μm) increases the arrhythmia threshold. Various concentrations of simvastatin increased fatigue, but it reached to significant level only at 30 μM. Conclusion: Simvastatin has potential anti-AVNRT effects by elevating arrhythmia threshold and prolongation of nodal refractoriness

Importance of analyzing the genomic instability in stem cell-based therapies

Stem cells are the main component in cell-based therapies and regenerative medicine to replace damaged tissues and cure various diseases. In regenerative medicine, in vitro stem cells’ culture is required for proliferation and differentiation. Although the risk of using these cells has not been established; but in addition to the possibility of spontaneous differentiation of undifferentiated cells after transplantation and teratoma formation, genome of these cells in culture media is instable and can be changed. Genomic instability can affect the transplantation safety of these cells or tissues derived from them. Genomic instability is one of the common features in stem cells and cancer. Hence, there is concern that the genomic instability during the manipulation of stem cells can be tumorigenic. Genomic instabilities are included in different sizes from point mutation to aneuploidy and mosaicism. Types of stem cells, culture conditions and some manipulation of cells such a long time are effective in creation and the rate of these instabilities. Therefore, in addition to optimizing the time and culture conditions, it is recommended to examine and follow the genomic abnormalities before therapeutic uses with appropriate methods

Human movement learning with dynamic movement primitives combined with mixture models

The proposed research is to provide a probabilistic approach to learn human movements. Dynamical Movement Primitives (DMP) have been extensively used in robotics in order to learn human motions [1]. The DMP modulates a virtual spring with a learned non-linear force profile /(x), perturbing the system to make it follow a desired trajectory

Effect of oral genistein administration in early and late phases of allergic encephalomyelitis

Objective(s): Experimental allergic encephalomyelitis (EAE) is an autoimmune disease validated as animal model of multiple sclerosis (MS). Administration of genistein, a phytoestrogenic component of soy, to mice at the onset of EAE is known to attenuate the clinical signs of the disease. The potential effects of genistein on established EAE is less studied. In the current study, we aimed to compare the effects of genistein administration on EAE severity in early and late phases of the disease. Materials and Methods: The C57BL/6 mice were induced with EAE, using MOG 35-55 and gavaged with genistein (300 mg/kg) either after the appearance of the first clinical sign or 30 days post disease induction for ten days. 24 hr after the last gavage, mice were sacrificed. Brains and spleens were removed for assessing lymphocyte proliferation, cell cytotoxicity, and cytokine profile. Spinal cords were dissected to assess the amount of demyelination using Luxol fast blue/cresyl violet staining. Results: Administering mice with genistein, after the establishment of EAE, did not reverse the clinical signs of disease. However, treating with genistein at the onset of disease alleviated the clinical signs by reducing neuronal demyelination. Genistein suppressed the production of IFN-γ and enhanced IL-10 secretion in splenocyte and brain. Genistein also reduced IL-12 and TNF-α secretion in splenocytes, suppressed the proliferation of T-cells, and reduced the cell cytotoxicity. Conclusion: Genistein oral therapy might only reduce EAE severity if started in early phases of the disease

The impact of conditional higher moments on risk management: The case of the tanker freight market

Tanker shipping provides the primary means of transportation for almost types of petroleum product traded globally. It is therefore essential to the energy supply chain to be able to correctly evaluate the structure and risk associated with freight rates in this market. This paper examines the concepts of conditional skewness and kurtosis in tanker freight rate. This is because, although the departure from normality of asset returns has been well documented, the relatively recent introduction of the concepts of conditional skewness and conditional kurtosis into the financial market literature, together with the unique shape of the supply curve in shipping markets, means that this has not been fully examined in the shipping literature. This is crucial given that a failure to take these structural characteristics into account could lead to market participants underestimating the probability of extreme and unfavourable events and therefore the consequent risk associated with market operations. Examining a sample of three types of tanker freight rate returns, we find that tanker freight rate returns exhibit conditional higher moments and that models that incorporate conditional skewness and kurtosis provide a more accurate value-at-risk measure and therefore a more accurate measure of the true risk faced by market participants

Detection of human papillomavirus DNA sequences in oral lesions using polymerase chain reaction

The purpose of the present study was to estimate the frequency of HPV DNA in four groups of oral lesions, including oral squamous cell carcinoma. Sixty paraffin-embedded oral tissue samples were examined for the presence of HPV DNAs using the PCR technique. These specimens were obtained from patients with oral squamous cell carcinoma (OSCC), leukoplakia, oral lichen planus (OLP), and pyogenic granuloma (PG). Consensus primers for L1 region (MY09 and MY11) and specific primers were used for detection of HPV DNA sequences in this study. we detected HPV DNA in 60% (9 out of 15) of OSCCs, 26.7% (4 out of 15) of leukoplakia, 13.3% (2 out of 15) of OLPs, and 6.7% (1 out of 15) of PGs. Statistical analysis showed that the prevalence of HPV in OSCC was significantly higher than other groups (P < 0.05). The frequency of HPV-16 and 18 detection in OSCC samples were 40% and 20%, respectively. The prevalence of these high risk HPVs was significantly higher in OSCC group (P < 0.05). The results of the present study show a successive increase of detection rate of HPV-16 and 18 DNAs from low level in samples of pyogenic granuloma and non-premalignant or questionably premalignant lesions of OLP to premalignant leukoplakia and to OSCC. © 2007 Tehran University of Medical Sciences. All rights reserved