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Shahi VK, Trivedi GS, Thampy SK, Rangarajan R. Studies on the electrochemical and permeation characteristics of asymmetric charged porous membranes. J Colloid Interface Sci 2003; 262:566-73. [PMID: 16256639 DOI: 10.1016/s0021-9797(03)00131-0] [Citation(s) in RCA: 95] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2002] [Accepted: 01/31/2003] [Indexed: 11/17/2022]
Abstract
Asymmetric charged porous membranes were prepared by imbedding 10% (W/W) ion-exchange resin in cellulose acetate binder. Membrane potential and conductance measurements have been carried out in sodium chloride solutions at different concentrations to investigate the relationship between concentration of fixed charges and electrochemical properties of developed nonselective cation- and anion-exchange membranes. Counterion transport number and permselectivity of these membranes were found to vary due to the presence of ion-exchange resin. The hydrodynamic and electroosmotic permeability of sodium chloride solutions has been studied in order to compute equivalent pore radius. For cation- and anion-exchange membranes good agreement was observed between pore radius values estimated from hydrodynamic and electroosmotic permeability coefficient separately, while for nonselective membranes no correlation was found. Membrane conductance data, along with values of concentration of fixed charges, were used for the estimation of the tortuosity factor, salt permeability coefficient, and frictional coefficient between solute and membrane matrix employing an interpretation by nonequilibrium thermodynamic principles based on frictional forces. Moreover, surface morphological studies of these membranes also have been carried out and the membranes were found to be reasonably homogeneous.
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Vyas PV, Ray P, Adhikary SK, Shah BG, Rangarajan R. Studies of the effect of variation of blend ratio on permselectivity and heterogeneity of ion-exchange membranes. J Colloid Interface Sci 2003; 257:127-34. [PMID: 16256464 DOI: 10.1016/s0021-9797(02)00025-5] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2002] [Accepted: 10/04/2002] [Indexed: 11/16/2022]
Abstract
Heterogeneous ion-exchange membranes (both cationic and anionic types) have been synthesized by solution casting techniques using polyvinyl chloride (PVC) as binder and ion-exchange resin (-300+400 mesh). The binder:resin ratio varied from 60:40 to 30:70. The transport behavior of the membranes has been evaluated chronopotentiometrically in sodium chloride (NaCl) solutions of different concentrations. The different parameters E(0) (potential drop across the membrane at the instant of application of current I), E(max) (maximum potential drop across the membrane after the application of current I), DeltaE (magnitude of the potential jump across the membrane at transition time tau), Itau(1/2), tau, etc., have been evaluated. The isoconductance points were determined and based on the microheterogeneous model proposed by Zabolotsky and Nikonenko (J. Membrane Sci. 79 (1993) 181) the distribution factors beta has been evaluated for both types of ion exchange membranes. The electroconductivity of the joint gel (kappa ) and pure gel phases (kappa ' ) has been determined. At any particular solution concentration the transport number as well as the permselectivity of membranes increases with increased resin content of the membrane. The microheterogeneity factor beta exhibits synchronization among the each set of four different membranes for both the cationic and anionic type.
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Vyas PV, Ray P, Rangarajan R, Adhikary SK. Electrical Conductance of Heterogeneous Cation-Exchange Membranes in Electrolyte Solutions. J Phys Chem B 2002. [DOI: 10.1021/jp021051g] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Vyas PV, Ray P, Trivedi GS, Adhikary SK, Rangarajan R. Studies on Exchange Equilibria of Cations between Cation-Exchange Membranes and Electrolytic Solutions. J Colloid Interface Sci 2002; 246:366-71. [PMID: 16290424 DOI: 10.1006/jcis.2001.8076] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2001] [Accepted: 10/29/2001] [Indexed: 11/22/2022]
Abstract
The variations of the selectivity coefficient K(A)(B) between Na(+)-H(+), Na(+)-K(+), and Na(+)-Cu(2+) systems and the separation factor alpha(A)(B) between Na(+)-Cu(2+) and K(+)-Cu(2+) systems in cation-exchange membranes as functions of loading and particle size of resin have been measured. The exchange affinities of all the membranes increase as H(+)<Na(+)<K(+)<Cu(2+). K(A)(B) is almost constant, independent of particle size and loading of resin in the membrane. Alpha(Na)(Cu) and alpha(K)(Cu) increase with decrease in particle size but remain almost constant with loading of resin in the membranes. The order of selectivity is K(Na)(H)<K(Na)(K)< or =K(Na)(Cu). The values of (alpha(A)(B)Q(0)(-1))(other)(alpha(A)(B)Q(0)(-1))(-1)(M(300)C60) for the Na(+)-Cu(2+) system are approximately 1.060 and for K(+)-Cu(2+) are approximately 0.870. Q(0) represents the exchange capacity of a dry membrane per unit volume (in milliequivalents per cubic centimeter).
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Shahi VK, Thampy SK, Siddhanta AK, Rangarajan R. SEPARATION OF SODIUM SULFATE ANDp-TOLUENE SULFONIC ACID BY ELECTRODIALYSIS. SEP SCI TECHNOL 2002. [DOI: 10.1081/ss-120006161] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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Rangarajan R, Courvoisier H, Gaul U. Dpp and Hedgehog mediate neuron-glia interactions in Drosophila eye development by promoting the proliferation and motility of subretinal glia. Mech Dev 2001; 108:93-103. [PMID: 11578864 DOI: 10.1016/s0925-4773(01)00501-9] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Neuron-glia interactions are crucial for the establishment of normal connectivity in the nervous system during development, but the molecular signals involved in these interactions are largely unknown. Here we show that differentiating photoreceptors in the developing Drosophila eye influence the proliferative and migratory behavior of the subretinal glia through the diffusible factors Decapentaplegic (Dpp) and Hedgehog (Hh). We demonstrate that proliferation and migration of the glia are separable processes, and that Dpp promotes both the proliferation and motility of the glia, whereas Hh appears to promote only their motility; neither specifies the direction of migration. We present evidence that Dpp and Hh act on the glia in parallel and through the regulation of transcription. Finally, we show that ectopic migration of subretinal glia can result in the ectopic projection of photoreceptor axons. Our study suggests a novel function for Hh in regulating migratory behavior and provides further evidence for a complex mutual dependence between glial and neuronal cells during development.
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Sivakumar M, Malaisamy R, Sajitha C, Mohan D, Mohan V, Rangarajan R. Preparation and performance of cellulose acetate–polyurethane blend membranes and their applications – II. J Memb Sci 2000. [DOI: 10.1016/s0376-7388(99)00339-7] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Shahi VK, Prakash R, Ramachandraiah G, Rangarajan R, Vasudevan D. Solution-Membrane Equilibrium at Metal-Deposited Cation-Exchange Membranes: Chronopotentiometric Characterization of Metal-Modified Membranes. J Colloid Interface Sci 1999; 216:179-184. [PMID: 10395776 DOI: 10.1006/jcis.1999.6292] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Copper- and lead-deposited interpolymer cationic membranes have been prepared by electroless plating by an ion-exchange method and characterized by chronopotentiometry and cyclic voltammetry. The parameters such as transition time (tau), Itau1/2, the potential drop (E0) across these membranes immediately after the application of constant current (I), and the height of the potential jump (DeltaE) across the membrane at tau have been measured by chronopotentiometry and compared with those of plain membranes. The approximate percentage of metal coverage and the number of ionic sites masked by the deposited metal in terms of NaCl concentration have been estimated from the differences in Itau1/2 values of plain and metal-deposited membranes. The quantity of metal deposited in a unit area of the membrane surface was measured by differential pulse polarography. The oxidation and reduction peak potentials corresponding to Cu(0)/Cu(II) and Pb(0)/Pb(II) couples were identified by cyclic voltammetry at pH 2.8 and 4.5 of 0.2 M CH3COONa-H2SO4. Copyright 1999 Academic Press.
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Abstract
Although glial cells have been implicated widely in the formation of axon tracts in both insects and vertebrates, their specific function appears to be context-dependent, ranging from providing essential guidance cues to playing a merely facilitory role. Here we examine the role of the retinal basal glia (RBG) in photoreceptor axon guidance in Drosophila. The RBG originate in the optic stalk and have been thought to migrate into the eye disc along photoreceptor axons, thus precluding any role in axon guidance. Here we show the following. (1) The RBG can, in fact, migrate into the eye disc even in the absence of photoreceptor axons in the optic stalk; they also migrate to ectopic patches of differentiating photoreceptors without axons providing a continuous physical substratum. This suggests that glial cells are attracted into the eye disc not through haptotaxis along established axons, but through another mechanism, possibly chemotaxis. (2) If no glial cells are present in the eye disc, photoreceptor axons are able to grow and direct their growth posteriorly as in wild type, but are unable to enter the optic stalk. This indicates that the RBG have a crucial role in axon guidance, but not in axonal outgrowth per se. (3) A few glia close to the entry of the optic stalk suffice to guide the axons into the stalk, suggesting that glia instruct axons by local interaction.
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Shahi V, Thampy S, Rangarajan R. Studies on transport properties of surfactant immobilized anion-exchange membrane. J Memb Sci 1999. [DOI: 10.1016/s0376-7388(99)00029-0] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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36
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Gong Q, Rangarajan R, Seeger M, Gaul U. The netrin receptor frazzled is required in the target for establishment of retinal projections in the Drosophila visual system. Development 1999; 126:1451-6. [PMID: 10068638 DOI: 10.1242/dev.126.7.1451] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Retinal axons in Drosophila make precise topographic connections with their target cells in the optic lobe. Here we investigate the role of the Netrins and their receptor Frazzled in the establishment of retinal projections. We find that the Netrins, although expressed in the target, are not required for retinal projections. Surprisingly, Frazzled, found on both retinal fibers and target cells, is required in the target for attracting retinal fibers, while playing at best a redundant role in the retinal fibers themselves; this finding demonstrates that target attraction is necessary for topographic map formation. Finally, we show that Frazzled is not required for the differentiation of cells in the target. Our data suggest that Frazzled does not function as a Netrin receptor in attracting retinal fibers to the target; nor does it seem to act as a homotypic cell adhesion molecule. We favor the possibility that Frazzled in the target interacts with a component on the surface of retinal fibers, possibly another Netrin receptor.
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Muthuswamy J, Tran P, Rangarajan R, Lenz FA, Hanley DF, Thakor NV. Somatosensory stimulus entrains spindle oscillations in the thalamic VPL nucleus in barbiturate anesthetized rats. Neurosci Lett 1999; 262:191-4. [PMID: 10218888 DOI: 10.1016/s0304-3940(99)00081-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
This study reports the effect of external stimuli on spindle oscillations in the somatosensory thalamus of barbiturate anesthetized rats. Multi-unit responses to somatosensory stimuli were measured from the contralateral thalamic ventral posterior lateral (VPL) nucleus at different stimulus strengths and periods. Spindle oscillations could be entrained by the somatosensory stimuli at periods between 2 and 5 s. A resonance phenomenon described as a quiescent pre-stimulus period followed by entrained post-stimulus oscillations, was observed for somatosensory stimuli above the threshold for eliciting cortical evoked potentials and a stimulus period between 2 and 5 s. This study demonstrates an ascending pathway for localized modulation of spindle oscillations.
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Warren JT, Chandrasekhar A, Kanki JP, Rangarajan R, Furley AJ, Kuwada JY. Molecular cloning and developmental expression of a zebrafish axonal glycoprotein similar to TAG-1. Mech Dev 1999; 80:197-201. [PMID: 10072788 DOI: 10.1016/s0925-4773(98)00215-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
TAG-1 is a mammalian cell adhesion molecule of the immunoglobulin superfamily that is expressed transiently by a subset of neurons and serves as a fertile substrate for neurite outgrowth in vitro (Furley, A.H., Morton, S.B., Manalo, D., Karagogeos, S., Dodd, H., Jessell, T.M., 1990 The axonal glycoprotein TAG-1 is an immunoglobulin superfamily member with neurite outgrowth promoting activity. Cell 61, 157-170). In order to examine the in vivo function of this molecule, we have cloned a zebrafish tag1-like cDNA and analyzed its expression patterns. tag1 Is expressed transiently by specific subsets of neurons when they are projecting their axons or when they are migrating. The specific and dynamic pattern of expression of zebrafish tag1 is consistent with its proposed role in axon guidance and cell migration.
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Park JK, Tran PH, Chao JK, Ghodadra R, Rangarajan R, Thakor NV. In vivo nitric oxide sensor using non-conducting polymer-modified carbon fiber. Biosens Bioelectron 1998; 13:1187-95. [PMID: 9871974 DOI: 10.1016/s0956-5663(98)00078-5] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Nitric oxide (NO) is emerging as a very important and ubiquitous gaseous messenger in the body. The response characteristics of NO sensors made of non-conducting polymer modified carbon fiber electrodes are investigated to determine their selectivity, sensitivity, and stability for in vivo use. A composite polymer, comprising Nafion, m-phenylenediamine, and resorcinol, showed the best selectivity and stability to amperometric NO detection. The non-conducting, self-limiting polymer film protects the electrode from interference and fouling by other biochemicals. Although the relative sensitivity to NO of the modified sensor is lower than that of the unmodified carbon fiber electrodes (less than 6%), the composite polymer electrode showed high selectivity against ascorbic acid (> 2000:1), nitrite (> 600:1), and dopamine (> 200:1). The stability of the NO sensor was maintained for at least 1 week. The NO sensitivity after in vivo experiments (n = 8) is 88.1 +/- 5.6% of initial sensitivity data obtained before in vivo experiments. Preliminary in vivo experiments done with this electrode are shown to capture elevated NO levels in brain following an ischemic injury.
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Sivakumar M, Mohan D, Rangarajan R. Preparation and performance of cellulose acetate-polyurethane blend membranes and their applications. Part 1. POLYM INT 1998. [DOI: 10.1002/(sici)1097-0126(199811)47:3<311::aid-pi51>3.0.co;2-2] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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42
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Sivakumar M, Mohanasundaram AK, Mohan D, Balu K, Rangarajan R. Modification of cellulose acetate: Its characterization and application as an ultrafiltration membrane. J Appl Polym Sci 1998. [DOI: 10.1002/(sici)1097-4628(19980314)67:11<1939::aid-app13>3.0.co;2-p] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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43
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Trivedi G, Shah B, Adhikary S, Indusekhar V, Rangarajan R. Studies on bipolar membranes. Part II — Conversion of sodium acetate to acetic acid and sodium hydroxide. REACT FUNCT POLYM 1997. [DOI: 10.1016/s1381-5148(96)00088-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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44
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Kim J, Lopez JL, Nanopoulos DV, Rangarajan R. Enhanced supersymmetric corrections to top-quark production at the Fermilab Tevatron. PHYSICAL REVIEW. D, PARTICLES AND FIELDS 1996; 54:4364-4373. [PMID: 10021118 DOI: 10.1103/physrevd.54.4364] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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46
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Yavagal ST, Rangarajan R. Clinical profile of acute myocardial infarction in women. JOURNAL OF THE INDIAN MEDICAL ASSOCIATION 1994; 92:283-4. [PMID: 7814898] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Three hundred fifty women with acute myocardial infarction who formed 17% of total myocardial infarction cases admitted were studied. Only 7.7% were below 40 years. Infarction occurred mostly (80%) in postmenopausal period. History of previous illness was present in 73% cases. Risk factors were present in majority (75%) of the cases. Common risk factors in Indian women were hypertension in 49% cases and diabetes mellitus in 34% cases. None were using oral contraceptives and it occurred mostly (77%) in multiparous women. Majority (94%) presented with typical chest pain. Premonitory symptoms occurred in only a few patients (14%). Complications occurred more frequently in 40% cases. Mortality rate appears to be high (18%); the commonest cause being cardiogenic shock.
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Rangarajan R, Heller HC, Miller JD. Chloride channel block phase advances the single-unit activity rhythm in the SCN. Brain Res Bull 1994; 34:69-72. [PMID: 8193935 DOI: 10.1016/0361-9230(94)90188-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The mammalian suprachiasmatic nuclei (SCN) contain a circadian pacemaker that exhibits a 24 h rhythm in single-unit activity in vivo and in vitro. Chloride channel block by a saturating concentration of picrotoxin at either CT6 or CT15 produces large phase advances in the SCN single-unit activity rhythm in vitro. These phase advances are not affected by simultaneous blockade of voltage-sensitive sodium and calcium channels by TTX and magnesium. Thus, the effects of picrotoxin appear to be mediated by direct blockade of the chloride channel, rather than subsequent membrane depolarization. GABA-A receptor-mediated chloride flux may be part of the mechanism of circadian timekeeping.
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Nirmal JD, Pandya VP, Desai NV, Rangarajan R. Cellulose Triacetate Membrane for Applications in Plating, Fertilizer, and Textile Dye Industry Wastes. SEP SCI TECHNOL 1992. [DOI: 10.1080/01496399208019467] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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49
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Falk T, Rangarajan R, Srednicki M. Dependence of density perturbations on the coupling constant in a simple model of inflation. PHYSICAL REVIEW. D, PARTICLES AND FIELDS 1992; 46:4232-4234. [PMID: 10014803 DOI: 10.1103/physrevd.46.4232] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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50
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Rangarajan R, Srednicki M. Chaotic dark matter. PHYSICAL REVIEW. D, PARTICLES AND FIELDS 1992; 46:3350-3351. [PMID: 10015281 DOI: 10.1103/physrevd.46.3350] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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