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Homocysteine-induced macrophage inflammatory protein-2 production by glomerular mesangial cells is mediated by PI3 Kinase and p38 MAPK
Suresh Shastry, Leighton R James
Journal of Inflammation , 2009, DOI: 10.1186/1476-9255-6-27
Abstract: Primary rat glomerular mesangial cells (MC, passage 8 to 15), isolated by standard sieving methodology, were exposed to Hcy (15, 50 or 100 μM) with L-cysteine (L-Cys; 100 μM) serving as a control. An antibody array was used to identify cytokines that were modulated when MCs were exposed to Hcy. Gene expression was assessed by quantitative RT-PCR, while western blotting analysis was used to assess cellular protein levels in the presence and absence of inhibitors of MAPK and PI3 Kinase. Finally, leukocyte adhesion assay was used to examine the effect of Hcy on leukocyte adhesion to glomerular MCs that were maintained in media without, and with, kinase inhibitors.We identified macrophage inflammatory protein 2 (MIP-2) as a key cytokine that manifested increases in both protein and mRNA following exposure of glomerular MC to pathophysiologic Hcy levels (50 μM). Further analyses revealed that Hcy-induced MIP-2 was dependent on activation of p38 MAPK and PI3 kinase. MIP-2 enhanced leukocyte adhesion to MC and this MIP-2-enhanced leukocyte adhesion was also dependent on activation of p38 MAPK and PI3K. Finally, we demonstrate that leukocyte adhesion to MC is specifically inhibited by anit-MIP2 antibody.The data suggest that Hcy participates in inflammatory cytokines production by glomerular MC and that Hcy-induced MIP-2 mediates leukocyte adhesion to MC.Elevated levels of plasma homocysteine (Hcy; ≥15 μM) are associated with chronic kidney disease and end-stage renal disease (ESRD) irrespective of the underlying aetiology [1,2]. However, the pathophysiological consequences of hyperhomocysteinemia (Hhcy) remain controversial because, although Hhcy has consistently been associated with morbidity and mortality, recent epidemiologic studies have produced conflicting results. In a prospective community-based study of persons without kidney disease at study inception, over a 5-year period, chronic kidney disease risk was found to increase in association with escalating Hcy level
The Kelvin Formula for Thermopower
Michael R. Peterson,B. Sriram Shastry
Physics , 2010, DOI: 10.1103/PhysRevB.82.195105
Abstract: Thermoelectrics are important in physics, engineering, and material science due to their useful applications and inherent theoretical difficulty, especially in strongly correlated materials. Here we reexamine the framework for calculating the thermopower, inspired by ideas of Lord Kelvin from 1854. We find an approximate but concise expression, which we term as the Kelvin formula for the the Seebeck coefficient. According to this formula, the Seebeck coefficient is given as the particle number $N$ derivative of the entropy $\Sigma$, at constant volume $V$ and temperature $T$, $S_{\text{Kelvin}}=\frac{1}{q_e}\{\frac{\partial {\Sigma}}{\partial N} \}_{V,T}$. This formula is shown to be competitive compared to other approximations in various contexts including strongly correlated systems. We finally connect to a recent thermopower calculation for non-Abelian fractional quantum Hall states, where we point out that the Kelvin formula is exact.
Genetic risk factors and retinal ganglion cell degeneration in primary open-angle glaucoma (POAG): A bird’s eye view  [PDF]
Barkur S. Shastry
Advances in Bioscience and Biotechnology (ABB) , 2013, DOI: 10.4236/abb.2013.45082
Abstract: Glaucoma is an optic neuropathy and often associated with elevated intraocular pressure (IOP). It is the second leading cause of irreversible blindness worldwide and is characterized by the optic nerve degeneration and loss of retinal ganglion cells (RGCs). This may lead to loss of vision. The primary cause of glaucoma is unknown but several risk factors including elevated IOP and age have been suggested. In most population, primary open-angle glaucoma (POAG) is the most common type of glaucoma and is often associated with elevated IOP. Genetic analyses have identified at least 14 chromosomal loci but only three genes which when mutated can cause POAG have been well documented. These genes account for less than 5% of all POAG cases suggesting that more than 90% of the genetic contribution of POAG cases is unknown. RGC consists of cell body, axon and dendritic arbor and each of these three parts can independently degenerate. Several molecular signals such as oxidative stress, mitochondrial dysfunction, disruption of neurotrophic factor (NTF), dysfunction of immune system, glial activation and the release of tumor necrosis factor (TNF) have been found to be involved in the optic nerve degeneration. Therefore, therapies aimed at axonal and cell body protection may have a greater protective role in early or progressive glaucoma. In the future, an understanding of gene-gene and gene-environmental factor interaction as well as epigenetic regulation of gene expression by environmental factors may provide an opportunity to develop neuroprotective therapies and DNA based diagnostic tests.
On Quantum Solitons in the Sawtooth Lattice
Diptiman Sen,B. Sriram Shastry,R. E. Walstedt,R. Cava
Physics , 1995, DOI: 10.1103/PhysRevB.53.6401
Abstract: We study the sawtooth lattice of a coupled spin $1/2$ Heisenberg system, a variant of the railroad trestle lattice. The ground state of this system is two-fold degenerate with periodic boundary conditions and supports kink antikink excitations, which are distinct in this case, unlike the railroad trestle lattice. The resulting low temperature thermodynamics is compared with the recently discovered Delafossites $Y Cu O_{2.5} ~$.
Antiamnesic potentiality of Argyreia speciosa (Burm.f) Boj. in mice
Habbu P,Mahadevan K,Shastry R,Chilakwad S
International Journal of Green Pharmacy , 2010,
Abstract: Several ′rasayana′ herbs that are enlisted in Indian system of medicine have been in use for the treatment of age-related neurodegenerative disorders including Alzheimer′s disease (AD). Roots of Argyreia speciosa are used in several Ayurvedic preparations as brain tonic and nervine tonic. The present work was undertaken to justify the traditional claim of the plant as nootropic and antiamnesic agent in mice. The ethyl acetate and ethanolic fractions (EtAS) of roots were selected for the study. Exteroceptive behavioural models such as elevated plus maze and Water maze were used to assess the short-term memory, whereas, scopolamine and natural ageing- induced amnesia served as interoceptive models. The whole brain acetyl cholinesterase activity was measured to assess the effect of A. speciosa on the central cholinergic system. Scopolamine (0.4 mg/kg, i.p.) increased the transfer latency significantly ( P< 0.01) in young mice on the first and second day as compared to control indicating the impairment of memory. Pretreatment with EAAS (100 and 200 mg/kg, p.o.) significantly ( P< 0.01) attenuated scopolamine and ageing-induced amnesia. Escape latency time was recorded in the water maze model as an index of acquisition, and trials were conducted for 4 days. The mean time spent in target quadrant (TSTQ) during retrieval trial on fifth day was taken as the index of retrieval (memory). EAAS (100 and 200 mg/kg, p.o.) administered before the training trial (from day 1 to day 4), significantly ( P< 0.01) attenuated scopolamine and ageing-induced decrease in TSTQ during the retrieval test on the fifth day. EAAS (100 and 200 mg/kg, p.o.) significantly produced reduction in whole brain acetyl cholinesterase (AChE) activity of both young and aged mice thus exhibiting anti-AChE activity in whole brain homogenate compared to Piracetam, scopolamine and control groups of mice. The results indicate that A. speciosa has significant nootropic and antiamnesic activity, justifying its traditional use in Ayurveda.
Thermoelectric effects in a strongly correlated model for Na$_x$CoO$_2$
Michael R. Peterson,B. Sriram Shastry,Jan O. Haerter
Physics , 2007, DOI: 10.1103/PhysRevB.76.165118
Abstract: Thermal response functions of strongly correlated electron systems are of appreciable interest to the larger scientific community both theoretically and technologically. Here we focus on the infinitely correlated t-J model on a geometrically frustrated two-dimensional triangular lattice. Using exact diagonalization on a finite sized system we calculate the dynamical thermal response functions in order to determine the thermopower, Lorenz number, and dimensionless figure of merit. The dynamical thermal response functions is compared to the infinite frequency limit and shown to be very weak functions of frequency, hence, establishing the validity of the high frequency formalism recently proposed by Shastry for the thermopower, Lorenz number, and the dimensionless figure of merit. Further, the thermopower is demonstrated to have a low to mid temperature enhancement when the sign of the hopping parameter $t$ is switched from positive to negative for the geometrically frustrated lattice considered.
Exact Solution of a One-Dimensional Multicomponent Lattice Gas with Hyperbolic Interaction
Bill Sutherland,Rudolf A. R?mer,B. Sriram Shastry
Physics , 1994, DOI: 10.1103/PhysRevLett.73.2154
Abstract: We present the exact solution to a one-dimensional multicomponent quantum lattice model interacting by an exchange operator which falls off as the inverse-sinh-square of the distance. This interaction contains a variable range as a parameter, and can thus interpolate between the known solutions for the nearest-neighbor chain, and the inverse-square chain. The energy, susceptibility, charge stiffness and the dispersion relations for low-lying excitations are explicitly calculated for the absolute ground state, as a function of both the range of the interaction and the number of species of fermions.
Conservation laws in the continuum $1/r^2$ systems
Rudolf A. R?mer,B. Sriram Shastry,B. Sutherland
Physics , 1995, DOI: 10.1088/0305-4470/29/15/033
Abstract: We study the conservation laws of both the classical and the quantum mechanical continuum $1/r^2$ type systems. For the classical case, we introduce new integrals of motion along the recent ideas of Shastry and Sutherland (SS), supplementing the usual integrals of motion constructed much earlier by Moser. We show by explicit construction that one set of integrals can be related algebraically to the other. The difference of these two sets of integrals then gives rise to yet another complete set of integrals of motion. For the quantum case, we first need to resum the integrals proposed by Calogero, Marchioro and Ragnisco. We give a diagrammatic construction scheme for these new integrals, which are the quantum analogues of the classical traces. Again we show that there is a relationship between these new integrals and the quantum integrals of SS by explicit construction.
Exact Solution of a Repulsive Fermi Model With Enhanced Superconducting Correlations
H. R. Krishnamurthy,B. Sriram Shastry,IISc,Bangalore
Physics , 2000, DOI: 10.1103/PhysRevLett.84.4918
Abstract: We present the exact solution of a model of interacting fermions in any dimension with a pure repulsive interaction projecting out a given Cooper channel. The solution rests upon the infinite ranged character of the interaction in real space, leading to a functional integral that is dominated by a Gaussian term. The solution produces strong superconducting enhancements and quasi long ranged order in a channel that is not present in the Hamiltonian explicitly, but of the form given by arguments from order by projection.
Strong Correlations Produce the Curie-Weiss Phase of Na$_{x}$CoO$_2$
Jan O. Haerter,Michael R. Peterson,B. Sriram Shastry
Physics , 2006, DOI: 10.1103/PhysRevLett.97.226402
Abstract: Within the t-J model we study several experimentally accessible properties of the 2D-triangular lattice system Na$_x$CoO$_2$, using a numerically exact canonical ensemble study of 12 to 18 site triangular toroidal clusters as well as the icosahedron. Focusing on the doping regime of $x\sim0.7$, we study the temperature dependent chemical potential, specific heat, magnetic susceptibility and the dynamic Hall coefficient $R_H(T,\omega)$ as well as the magnetic field dependent thermopower. We find a crossover between two phases near $x \sim 0.75$ in susceptibility and field suppression of the thermopower arising from strong correlations. An interesting connection is found between the temperature dependence of the diamagnetic susceptibility and the Hall-coefficient. We predict a large thermopower enhancement, arising from {\em transport corrections} to the Heikes-Mott formula, in a model situation where the sign of hopping is reversed from that applicable to Na$_x$CoO$_2$.
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