545 research outputs found
Mitochondrial apoptosis induced by Chamaemelum nobile extract in breast cancer cells
Chamaemelum nobile (Asteraceae) commonly known as âčRoman chamomileâș is a medicinal plant used for numerous diseases in traditional medicine, although its anticancer activity is unknown. The present study was carried out to investigate the anticancer as well as apoptotic activity of ethyl acetate fraction of C. nobile on different cancerous cell lines. The cells were treated with varying concentrations (0.001-0.25 mg/mL) of this fraction for 24, 48 and 72 h. Apoptosis induced in MCF-7 cells following treatment with ethyl acetate fraction was measured using Annexin V/PI, flowcytometry and western blotting analysis. The results showed that C. nobile ethyl acetate fraction revealed relatively high antiproliferative activity on MCF-7 cells; however, it caused minimal growth inhibitory response in normal cells. The involvement of apoptosis as a major cause of the fraction-induced cell death was confirmed by annexin-V/PI assay. In addition, ethyl acetate fraction triggered the mitochondrial apoptotic pathway by decreasing the Bcl-2 as well as increasing of Bax protein expressions and subsequently increasing Bax/Bcl-2 ratio. Furthermore, decreased proliferation of MCF-7 cells in the presence of the fraction was associated with G2/M phase cell cycle arrest. These findings confirm that ethyl acetate fraction of C.nobile may contain a diversity of phytochemicals which suppress the proliferation of MCF-7 cells by inducing apoptosis. © 2016 by School of Pharmacy Shaheed Beheshti University of Medical Sciences and Health Services
NXSensor web tool for evaluating DNA for nucleosome exclusion sequences and accessibility to binding factors
Nucleosomes, a basic structural unit of eukaryotic chromatin, play a significant role in regulating gene expression. We have developed a web tool based on DNA sequences known from empirical and theoretical studies to influence DNA bending and flexibility, and to exclude nucleosomes. NXSensor (available at ) finds nucleosome exclusion sequences, evaluates their length and spacing, and computes an âaccessibility scoreâ giving the proportion of base pairs likely to be nucleosome-free. Application of NXSensor to the promoter regions of housekeeping (HK) genes and those of tissue-specific (TS) genes revealed a significant difference between the two classes of gene, the former being significantly more open, on average, particularly near transcription start sites (TSSs). NXSensor should be a useful tool in assessing the likelihood of nucleosome formation in regions involved in gene regulation and other aspects of chromatin function
Entropy of 4D extremal black holes
We derive the Bekenstein-Hawking entropy formula for four-dimensional Reissner-Nordstr\"om extremal black holes in type II string theory. The derivation is performed in two separate (T-dual) weak coupling pictures. One uses a type IIB bound state problem of D5- and D1-branes, while the other uses a bound state problem of D0- and D4-branes with macroscopic fundamental type IIA strings. In both cases the D-brane systems are also bound to a Kaluza-Klein monopole, which then yields the four-dimensional black hole at strong coupling
Is string theory a theory of strings?
Recently a great deal of evidence has been found indicating that type IIA string theory compactified on K3 is equivalent to heterotic string theory compactified on T^4. Under the transformation which relates the two theories, the roles of fundamental and solitonic string solutions are interchanged. In this letter we show that there exists a solitonic membrane solution of the heterotic string theory which becomes a singular solution of the type IIA theory, and should therefore be interpreted as a fundamental membrane in the latter theory. We speculate upon the implications that the complete type IIA theory is a theory of membranes, as well as strings
Surface Crack Characterization: Geometry and Stress Intensity Factor Measurements
The reflection coefficient of a Rayleigh wave at a surface crack is measured in both the long wavelength and the short wavelength limits. from the long wavelength measurement, the maximum value of the stress intensity factor is evaluated. Using glass samples, we have formed surface cracks, measured their reflection coefficient, and predicted failure stress with an error of less than 5% from the measured fracture stress. In short wavelength limit, the reflection coefficient is measured versus frequency. Length and depth resonances of the crack are observed and used to estimate the crack geometry with an accuracy of 10-20% for EDM notches in steel
Total Widths And Slopes From Complex Regge Trajectories
Maximally complex Regge trajectories are introduced for which both Re
and Im grow as ( small and
positive). Our expression reduces to the standard real linear form as the
imaginary part (proportional to ) goes to zero. A scaling formula for
the total widths emerges: constant for large M, in very
good agreement with data for mesons and baryons. The unitarity corrections also
enhance the space-like slopes from their time-like values, thereby resolving an
old problem with the trajectory in charge exchange. Finally, the
unitarily enhanced intercept, , \nolinebreak is in
good accord with the Donnachie-Landshoff total cross section analysis.Comment: 9 pages, 3 Figure
Scattering of Four-Dimensional Black Holes
The moduli space metric for an arbitrary number of extremal black holes in
four dimensions with arbitrary relatively supersymmetric charges is found.Comment: 16 pages, REVTeX; references adde
Infrared renormalons and analyticity structure in pQCD
Relation between the infrared renormalons, the Borel resummation
prescriptions, and the analyticity structure of Green functions in perturbative
QCD (pQCD) is investigated. A specific recently suggested Borel resummation
prescription resulted in the Principal Value and an additional power-suppressed
correction that is consistent with the Operator Product Expansion. Arguments
requiring the finiteness of the result for any power coefficient of the leading
infrared renormalon, and the consistency in the case of the absence of that
renormalon, require that this prescription be modified. The apparently most
natural modification leads to the result represented by the Principal Value.
The analytic structure of the amplitude in the complex coupling plane, obtained
in this way, is consistent with that obtained in the literature by other
methods.Comment: 6 pages, revtex4, 1 eps-figure; improved version - the paragraph
containing Eqs.(18) and (19) is new, as well as the next paragraph; the Title
modified; some references added; version to appear in Phys. Rev.
Curvature-corrected dilatonic black holes and black hole -- string transition
We investigate extremal charged black hole solutions in the four-dimensional
string frame Gauss-Bonnet gravity with the Maxwell field and the dilaton.
Without curvature corrections, the extremal electrically charged dilatonic
black holes have singular horizon and zero Bekenstein entropy. When the
Gauss-Bonnet term is switched on, the horizon radius expands to a finite value
provided curvature corrections are strong enough. Below a certain threshold
value of the Gauss-Bonnet coupling the extremal black hole solutions cease to
exist. Since decreasing Gauss-Bonnet coupling corresponds to decreasing string
coupling , the situation can tentatively be interpreted as classical
indication on the black hole -- string transition. Previously the extremal
dilaton black holes were studied in the Einstein-frame version of the
Gauss-Bonnet gravity. Here we work in the string frame version of this theory
with the S-duality symmetric dilaton function as required by the heterotic
string theory.Comment: 14 pages, 2 figure
Rotating Black Holes which Saturate a Bogomol'nyi Bound
We construct and study the electrically charged, rotating black hole solution
in heterotic string theory compactified on a dimensional torus. This
black hole is characterized by its mass, angular momentum, and a
dimensional electric charge vector. One of the novel features of this solution
is that for , its extremal limit saturates the Bogomol'nyi bound. This is
in contrast with the case where the rotating black hole solution develops
a naked singularity before the Bogomol'nyi bound is reached. The extremal black
holes can be superposed, and by taking a periodic array in , one obtains
effectively four dimensional solutions without naked singularities.Comment: 13 pages, no figure
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