85 research outputs found
T and S dualities and The cosmological evolution of the dilaton and the scale factors
Cosmologically stabilizing radion along with the dilaton is one of the major
concerns of low energy string theory. One can hope that T and S dualities can
provide a plausible answer. In this work we study the impact of S and T duality
invariances on dilaton gravity. We have shown various instances where
physically interesting models arise as a result of imposing the mentioned
invariances. In particular S duality has a very privileged effect in that the
dilaton equations partially decouple from the evolution of the scale factors.
This makes it easy to understand the general rules for the stabilization of the
dilaton. We also show that certain T duality invariant actions become S duality
invariance compatible. That is they mimic S duality when extra dimensions
stabilize.Comment: Corrected a misleading interpretation of the S duality transformation
and a wrong comment on d=10. I thank A.Kaya for pointing this out to me in
time. So the new version is dealing with d=10 only. Added references and
corrected some typos. Minor re-editing. Omitted a section for elaboration in
a further study. Corrected further typo
Degravitation, Inflation and the Cosmological Constant as an Afterglow
In this report, we adopt the phenomenological approach of taking the
degravitation paradigm seriously as a consistent modification of gravity in the
IR, and investigate its consequences for various cosmological situations. We
motivate degravitation-- where Netwon's constant is promoted to a scale
dependent filter function-- as arising from either a small (resonant) mass for
the graviton, or as an effect in semi-classical gravity. After addressing how
the Bianchi identities are to be satisfied in such a set up, we turn our
attention towards the cosmological consequences of degravitation. By
considering the example filter function corresponding to a resonantly massive
graviton (with a filter scale larger than the present horizon scale), we show
that slow roll inflation, hybrid inflation and old inflation remain
quantitatively unchanged. We also find that the degravitation mechanism
inherits a memory of past energy densities in the present epoch in such a way
that is likely significant for present cosmological evolution. For example, if
the universe underwent inflation in the past due to it having tunneled out of
some false vacuum, we find that degravitation implies a remnant `afterglow'
cosmological constant, whose scale immediately afterwards is parametrically
suppressed by the filter scale () in Planck units . We discuss circumstances through which this scenario reasonably
yields the presently observed value for . We also
find that in a universe still currently trapped in some false vacuum state,
resonance graviton models of degravitation only degravitate initially Planck or
GUT scale energy densities down to the presently observed value over timescales
comparable to the filter scale.Comment: To appear in JCAP; sections discussing degravitation as a
semi-classical effect and the modified Bianchi identities adde
Supersymmetry Breaking and Dilaton Stabilization in String Gas Cosmology
In this Note we study supersymmetry breaking via gaugino condensation in
string gas cosmology. We show that the same gaugino condensate which is
introduced to stabilize the dilaton breaks supersymmetry. We study the
constraints on the scale of supersymmetry breaking which this mechanism leads
to.Comment: 11 page
Apigenin inhibits PMA-induced expression of pro-inflammatory cytokines and AP-1 factors in A549 cells
Acute and chronic alveolar or bronchial inflammation is thought to be central to the pathogenesis of many respiratory disorders. Cytokines and granulocyte macrophage colony-stimulating factors (GM-CSF) play an important role in chronic inflammation. Activator protein-1 (AP-1) the superfamily of transcription factors is involved in proliferation, differentiation, apoptosis, and transformation including inflammation. Understanding the function and regulation of proinflammatory factors involved in inflammation may provide the novel therapeutic strategies in the treatment of inflammatory diseases. Our aim of the present study is to investigate the pro-inflammatory cytokines and pattern of AP-1 factors expressed during activation of lung adenocarcinoma A549 cells by Phorbol-12-myristate-13-acetate (PMA) and to understand the anti-inflammatory effect of apigenin. A549 cells were treated with and without PMA or apigenin, and the cell viability was assessed by MTT assay. Expressions of inflammatory mediators and different AP-1 factors were analyzed by semi-quantitative RT-PCR. IL-6 protein secreted was analyzed by ELISA, and expressions of IL-1β, c-Jun, and c-Fos proteins were analyzed by Western blotting. Activation of A549 cells by PMA, induced the expression of pro-inflammatory cytokine (IL-1β, IL-2, IL-6, IL-8, and TNF-α) mRNAs and secretion of IL-6 and the expression of specific AP-1 factors (c-Jun, c-Fos, and Fra-1). Treatment of cells with apigenin, significantly inhibited PMA-stimulated mRNA expression of above pro-inflammatory cytokines, AP-1 factors, cyclooxygenase-2, and secretion of IL-6 protein. Results suggested that the AP-1 factors may be involved in inflammation and apigenin has anti-inflammatory effect, which may be useful for therapeutic management of lung inflammatory diseases. © 2015, Springer Science+Business Media New York
Unconventional Cosmology
I review two cosmological paradigms which are alternative to the current
inflationary scenario. The first alternative is the "matter bounce", a
non-singular bouncing cosmology with a matter-dominated phase of contraction.
The second is an "emergent" scenario, which can be implemented in the context
of "string gas cosmology". I will compare these scenarios with the inflationary
one and demonstrate that all three lead to an approximately scale-invariant
spectrum of cosmological perturbations.Comment: 45 pages, 10 figures; invited lectures at the 6th Aegean Summer
School "Quantum Gravity and Quantum Cosmology", Chora, Naxos, Greece, Sept.
12 - 17 2012, to be publ. in the proceedings; these lecture notes form an
updated version of arXiv:1003.1745 and arXiv:1103.227
Interplay of nuclear receptors (ER, PR, and GR) and their steroid hormones in MCF-7 cells
Steroid hormones and their nuclear receptors play a major role in the development and progression of breast cancer. MCF-7 cells are triple-positive breast cancer cells expressing estrogen receptor (ER), progesterone receptor (PR), and glucocorticoid receptor (GR). However, interaction and their role in expression pattern of activator protein (AP-1) transcription factors (TFs) are not completely understood. Hence, in our study, MCF-7 cells were used as an in vitro model system to study the interplay between the receptors and hormones. MCF-7 cells were treated with estradiol-17β (E2), progesterone (P4), and dexamethasone (Dex), alone or in combination, to study the proliferation of cells and expression of AP-1 genes. MTT assay results show that E2 or P4 induced the cell proliferation by more than 35 %, and Dex decreased the proliferation by 26 %. E2 and P4 are found to increase ERα by more than twofold and c-Jun, c-Fos, and Fra-1 AP-1 TFs by more than 1.7-fold, while Dex shows opposite effect of E2- or P4-induced effect as well as effect on the expression of nuclear receptors and AP-1 factors. E2 antagonist Fulvestrant (ICI 182,780) found to reduce proliferation and E2-induced expression of AP1-TFs, while P4 or Dex antagonist Mifepristone (RU486) is found to block GR-mediated expression of NRs and AP-1 mRNAs. Results suggest that E2 and P4 act synergistically, and Dex acts as an antagonist of E2 and P4
Aqueous areca nut extract induces oxidative stress in human lung epithelial A549 cells: Probable role of p21 in inducing cell death
Areca nut a well-known masticator used across globe. Habitual chewing of areca nut is associated with serious oral health effects. However, the role of areca nut in oxidative stress induction and cell death is less understood. Hence, in the present study we aimed to evaluate the toxic mechanism of areca nut extract on human lung epithelial A549 cells. Cells were treated with or without aqueous areca nut extract and cell viability was measured by MTT assay. Cells treated with areca nut extract show reduced viability in a dose dependent manner with the IC50 of 0.5 concentration. Areca nut extract induced the reactive oxygen species (ROS), lipid peroxidation followed by membrane damage with leakage of lactate dehydrogenase (LDH) enzyme. Cells with continuous exposure of areca nut extract depletes the free radical neutralizing anti-oxidant enzymes like superoxide dismutase (SOD), Glutathione peroxidase (GSH-Px) and Glutathione-S-transferase (GST). Further, the analysis of mRNA expression of apoptotic genes and cell cycle regulators show decreased expression of anti-apoptotic gene (Bcl-2), Cyclin E1, Cyclin D1, CDK4, Rb and p53 whereas induced expression of p21 and marginal increase of pro-apoptotic gene (Bax) confirms the toxic nature of areca nut. Thus, cell death due to areca nut exposure may be through different mechanism rather than the conventional apoptotic pathway, where p21 induction might be independent of p53 action, which possibly suggests that there may be a role of p21 in oxidative stress induced cell death. Further FACS analysis confirms cell death in areca nut treated cells. © 2016 Elsevier Inc
Cadmium induces oxidative stress and apoptosis in lung epithelial cells
Cadmium (Cd) is one of the well-known highly toxic environmental and industrial pollutants. Cd first accumulates in the nucleus and later interacts with zinc finger proteins of antiapoptotic genes and inhibit the binding of transcriptional factors and transcription. However, the role of Cd in oxidative stress and apoptosis is less understood. Hence, the present study was undertaken to unveil the mechanism of action. A549 cells were treated with or without Cd and cell viability was measured by MTT assay. Treatment of cells with Cd shows reduced viability in a dose-dependent manner with IC50 of 45 μM concentration. Cd significantly induces the reactive oxygen species (ROS), lipid peroxidation followed by membrane damage with the leakage of lactate dehydrogenase (LDH). Cells with continuous exposure of Cd deplete the antioxidant super oxide dismutase (SOD) and glutathione peroxidase (GSH-Px) enzymes. Further, analysis of the expression of genes involved in apoptosis show that both the extrinsic and intrinsic apoptotic pathways were involved. Death receptor marker tumor necrosis factor-α (TNF-α), executor caspase-8 and pro-apoptotic gene (Bax) were induced, while antiapoptotic gene (Bcl-2) was decreased in Cd-treated cells. Fluorescence-activated cell sorting (FACS) analysis further confirms the induction of apoptosis in Cd-treated A549 cells
Differential expression of AP-1 transcription factors in human prostate LNCaP and PC-3 cells: role of Fra-1 in transition to CRPC status
Androgen receptor (AR) signaling axis plays a vital role in the development of prostate and critical in the progression of prostate cancer. Androgen withdrawal initially regresses tumors but eventually develops into aggressive castration-resistant prostate cancer (CRPC). Activator Protein-1 (AP-1) transcription factors are most likely to be associated with malignant transformation in prostate cancer. Hence, to determine the implication of AR and AP-1 in promoting the transition of prostate cancer to the androgen-independent state, we used AR-positive LNCaP and AR-negative PC-3 cells as an in vitro model system. The effect of dihydrotestosterone or anti-androgen bicalutamide on the cell proliferation and viability was assessed by MTT assay. Expression studies on AR, marker genes-PSA, TMPRSS2, and different AP-1 factors were analyzed by semi-quantitative RT-PCR and expressions of AR and Fra-1 proteins were analyzed by Western blotting. Dihydrotestosterone induced the cell proliferation in LNCaP with no effect on PC-3 cells. Bicalutamide decreased the viability of both LNCaP and PC-3 cells. Dihydrotestosterone induced the expression of AR, PSA, c-Jun, and Fra-1 in LNCaP cells, and it was c-Jun and c-Fos in case of PC-3 cells, while bicalutamide decreased their expression. In addition, constitutive activation and non-regulation of Fra-1 by bicalutamide in PC-3 cells suggested that Fra-1, probably a key component, involved in transition of aggressive androgen-independent PC-3 cells with poor prognosis. © 2017, Springer Science+Business Media New York
Looking Beyond Inflationary Cosmology
In spite of the phenomenological successes of the inflationary universe
scenario, the current realizations of inflation making use of scalar fields
lead to serious conceptual problems which are reviewed in this lecture. String
theory may provide an avenue towards addressing these problems. One particular
approach to combining string theory and cosmology is String Gas Cosmology. The
basic principles of this approach are summarized.Comment: invited talk at "Theory Canada 1" (Univ. of British Columbia,
Vancouver, Canada, June 2 - 4, 2005) (references updated
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