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  • Chemistry  (2)
  • Multiphase, Granular, and Particle-Laden Flows  (2)
  • SDS-PAGE  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Pb-induced alterations in tyrosine hydroxylase activity in rat brain (1997)
    Springer
    Molecular and cellular biochemistry 175 (1997), S. 137-141 
    Details
    ISSN: 1573-4919
    Keywords: Pb ; dopamine biosynthesis ; tyrosine hydroxylase ; brain ; SDS-PAGE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Our previous studies have shown that exposure to low levels of Pb results in significant reductions in dopamine (DA) and its metabolites (3,4-dihyroxyphenylacetic acid, DOPAC and homovanillic acid, HVA) in nucleus acumbens (NA). This area of brain receives dopaminergic projections from the ventral tegmentum and is considered vital in manifestation of many behavioral responses. Similarly, basal and K+-induced release of DA was found significantly reduced in the Pb-exposed rats as compared to the controls in this brain region. Additional studies indicated that acute infusion of Pb in nucleus acumbens caused significant release of DA. Based on these observations it was postulated that the reductions in DA contents and in the basal and stimulus-induced release of DA in NA were manifestations of attenuated dopaminergic activity in this brain region. However, the mechanism of this attenuation is not yet clear. Studies reported here were designed to evaluate the role of a key regulatory enzy me in biosynthesis of DA, i.e. tyrosine hydroxylase (TH) in Pb-induced reductions in dopaminergic activity. The results of these studies indicated that 50 and 500 ppm Pb produced 22.8 and 56% inhibition of TH activity in vitro respectively, and that the enzyme activity was reduced to 43% in rats exposed to 50 ppm lead for 30 days as compared to the controls. The alterations in TH activity in Pb-exposed animals were further confirmed by Western blot analysis. Collectively, these results suggest that Pb-induced inhibition of TH activity in rat brain may contribute to the reductions in dopaminergic activity observed in Pb-exposed animals. (Mol Cell Biochem 175: 137–141, 1997)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006891830182
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  • 2
    Electronic Resource
    Electronic Resource
    Region - specific alterations in tyrosine hydroxylase activity in rats exposed to lead (1998)
    Springer
    Molecular and cellular biochemistry 189 (1998), S. 19-24 
    Details
    ISSN: 1573-4919
    Keywords: brain ; pb ; tyrosine hydroxylase ; SDS-PAGE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Previous studies from our laboratory showed that subchronic exposure to low levels of Pb resulted in significant decrease in dopamine (DA) content, attenuation of stimulus-induced release of DA in the dopaminergic projection area of nucleus accumbens (NA), and alterations in tyrosine hydroxylase (TH) activity in rat whole brain homogenates. The present study reported here was conducted to assess the functional integrity of DA synthesis in different brain regions of rats subchronically (90-days) exposed to 50 ppm Pb by measuring the activity of the rate limiting enzyme, tyrosine hydroxylase, in seven brain regions. In Pb-exposed rats, TH activity was reduced in two of the seven brain regions investigated, i.e., nucleus accumbens (42% reduction) and frontal cortex (61% reduction) when compared to controls. In contrast, Pb exposure did not affect the TH activity in cerebellum, brainstem, hippocampus, hypothalamus and striatum. The changes in TH activity in nucleus accumbens (NA) and frontal cortex (FC) in Pb-exposed rats were further confirmed by Western blot analysis using TH polyclonal antibody. Collectively, these results indicate that low level subchronic Pb exposure may affect TH protein in these brain regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006896111280
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  • 3
    Electronic Resource
    Electronic Resource
    The foldability landscape of model proteins (1997)
    New York : Wiley-Blackwell
    Biopolymers 42 (1997), S. 427-438 
    Details
    ISSN: 0006-3525
    Keywords: protein folding ; molecular evolution ; lattice models ; fitness landscapes ; spin glasses ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular evolution may be considered as a walk in a multidimensional fitness landscape, where the fitness at each point is associated with features such as the function, stability, and survivability of these molecules. We present a simple model for the evolution of protein sequences on a landscape with a precisely defined fitness function. We use simple lattice models to represent protein structures, with the ability of a protein sequence to fold into the structure with lowest energy, quantified as the foldability, representing the fitness of the sequence. The foldability of the sequence is characterized based on the spin glass model of protein folding. We consider evolution as a walk in this foldability landscape and study the nature of the landscape and the resulting dynamics. Selective pressure is explicitly included in this model in the form of a minimum foldability requirement. We find that different native structures are not evenly distributed in interaction space, with similar structures and structures with similar optimal foldabilities clustered together. Evolving proteins marginally fulfill the selective criteria of foldability. As the selective pressure is increased, evolutionary trajectories become increasingly confined to “neutral networks,” where the sequence and the interactions can be significantly changed while a constant structure is maintained. © 1997 John Wiley & Sons, Inc. Biopoly 42: 427-438, 1997
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Searching for foldable protein structures using optimized energy functions (1995)
    New York : Wiley-Blackwell
    Biopolymers 36 (1995), S. 43-51 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During evolution, the effective interactions between residues in a protein can be adjusted through mutations to allow the protein to fold to its native structure on an adequate time scale. We seek to address the question: Are there some structures that can be better optimized than others? Using exhaustive enumeration of the compact conformations of short proteins confined to simple lattices, we find that the best structures are those that contain contacts rare in random structures, indicating the importance of nonlocal contacts for assisting the folding process. Certain structural motifs such as long β-hairpins, Greek-key motifs, and jelly rolls, commonly found in proteins of known structure, have a high degree of optimizability. Contrary to what might be expected, positive correlations between the various interactions reduce optimizability. The optimization procedure produces a correlated energy landscape, which might assist folding. © 1995 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360360105
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  • 5
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    Caustics-induced coalescence of small droplets near a vortex (2017)
    American Physical Society (APS)
    Details
    Publication Date: 2017-03-02
    Description: Author(s): P. Deepu, S. Ravichandran, and Rama Govindarajan A simple model of droplets being centrifuged out of a vortex shows that caustics lead to a rapid formation of large drops through coalescence. Polydispersity in droplet size enhances this process. [Phys. Rev. Fluids 2, 024305] Published Tue Feb 28, 2017
    Keywords: Multiphase, Granular, and Particle-Laden Flows
    Electronic ISSN: 2469-990X
    Topics: Physics
    Published by American Physical Society (APS)
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  • 6
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    Solid-on-solid contact in a sphere-wall collision in a viscous fluid (2018)
    American Physical Society (APS)
    Details
    Publication Date: 2018-04-10
    Description: Author(s): Sumit Kumar Birwa, G. Rajalakshmi, Rama Govindarajan, and Narayanan Menon New experiments show that collisions between a sphere and a plane immersed in a viscous fluid involve direct mechanical contact, in contrast to expectations based on earlier theory. An electrical probe is used to monitor short-time mechanics of contact formation during the rebound of the sphere. [Phys. Rev. Fluids 3, 044302] Published Mon Apr 09, 2018
    Keywords: Multiphase, Granular, and Particle-Laden Flows
    Electronic ISSN: 2469-990X
    Topics: Physics
    Published by American Physical Society (APS)
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