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6 results on '"Suresh Chand Tyagi"'

1. Ablation of matrix metalloproteinase-9 prevents cardiomyocytes contractile dysfunction in diabetics

Author

Priyanka ePrathipati, Naira eMetreveli, Shyam Sundar Nandi, Suresh Chand Tyagi, and Paras Kumar eMishra

Subjects
Diabetes Mellitus, Heart Failure, Calcium transient, Akita, Serca-2a, Physiology, QP1-981
Abstract

Elevated expression and activity of matrix metalloproteinase-9 (MMP9) and decreased contractility of cardiomyocytes are documented in diabetic hearts. However, it is unclear whether MMP is involved in the regulation of contractility of cardiomyocytes in diabetic hearts. In the present study, we tested the hypothesis that MMP9 regulates contractility of cardiomyocytes in diabetic hearts, and ablation of matrix metalloproteinase-9 (MMP9) prevents impaired contractility of cardiomyocytes in diabetic hearts. To determine the specific role of MMP9 in cardiomyocyte contractility, we used twelve - fourteen week male WT (normoglycemic sibling of Akita), Akita, and Ins2+/- /MMP9-/- (DKO) mice. DKO mice were generated by cross-breeding male Ins2+/- Akita (T1D) with female MMP9 knockout (MMP9-/-) mice. We isolated cardiomyocytes from the heart of the above three groups of mice and measured their contractility and calcium transients. Moreover, we determined mRNA and protein levels of sarco-endoplasmic reticulum calcium ATPase-2a (SERCA-2a), which is involved in calcium handling during contractility of cardiomyocytes, in WT, Akita, and DKO hearts using qPCR, Western blotting and immunoprecipitation, respectively. Our results revealed that in Akita hearts where increased expression and activity of MMP9 is reported, the rates of shortening and re-lengthening (± dL/dt) of cardiomyocytes were decreased, time to 90% peak height and baseline during contractility was increased, rate of calcium decay was increased, and calcium transient was decreased as compared to WT cardiomyocytes. However, these changes in Akita were blunted in DKO cardiomyocytes. The molecular analyses of SERCA-2a in the hearts showed that it was downregulated in Akita as compared to WT but was comparatively upregulated in DKO. These results suggest that abrogation of MMP9 gene prevents contractility of cardiomyocytes, possibly by increasing SERCA-2a and calcium transients. We conclude that MMP9 plays crucial role in the regulation of contractility of cardiomyocytes in diabetic hearts.

Published
2016
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2. Studies on the kinetics and mechanism of the interaction of hexaaquochromium(III) with acetate ions

Author

A. Aziz Khan and Suresh Chand Tyagi

Subjects
Reaction rate constant, Polymers and Plastics, Ligand, Chemistry, Inorganic chemistry, Kinetics, Materials Chemistry, Physical chemistry, Rate equation, Eyring equation, Conductivity, Kinetic energy, Ion
Abstract

The composition of the complex formed by the interaction of hexaaquochromium(III) with acetate ions was determined by Job's method of continuous variations and by conductivity measurements. It was found to be (1:2). Kinetic studies were carried out at 30, 35 and 40°C while the [H+] of the medium was varied from 0.1 × 10−4 M to 31.6 × 10−4 M. The variation of the pseudo-first order rate constant (kobs) with [H+] and the ligand concentration indicated a mechanism based on ion-pair formation and the following rate equation was derived on this basis: kobs=[kanKIKa[H+]+k′anK′IKa][acetate]T[H+]2[H+]Ka+[H+]K′I+KaK′I+[KIKa+[H+]+K′IK′aKa][acetate]T The reaction was found to be of the associative interchange (Ia) type for the reaction of Cr(H2O)63+ and dissociative interchange (Id) type for that of Cr(H2O)5OH2+ with acetate ions. The activation parameters, calculated using the Eyring equation are: ΔH∗ = 103 kJ mol−1; ΔS∗ = 31 JK−1mol−1 for the formation of Cr(H2O)5(OOCCH3)2+ and ΔH = 104 kJ mol−1; ΔS∗ = 41(±2)JK−1mol−1 for the formation of Cr(H2O)4OH(OOCCH3)+.

Published
1979

3. The studies on the composition and kinetics of the complex formed by the interaction of hexaaquochromium(III) with salicylic acid

Author

Suresh Chand Tyagi and A. Aziz Khan

Subjects
Polymers and Plastics, Chemistry, Ligand, Inorganic chemistry, Kinetics, Rate equation, chemistry.chemical_compound, Reaction rate constant, Ionic strength, Mole, Materials Chemistry, Physical chemistry, Eyring equation, Salicylic acid
Abstract

The interaction of hexaaquochromium(III) with salicylic acid was studied in the pH range 2.5-4.2. The composition of the complex formed was one mole of salicylic acid to one mole of hexaaquochromium(III). The variation of pseudo first order rate constant with pH, ionic strength and ligand concentrations indicated a mechanism based on ion-pair formation. The rate equation derived on the basis of this mechanism is: k obs = k an K 1 K a [salicylic] T [H + +K a +K 1 K a [salicylic] T An associative interchange mechanism is suggested for the reaction. The activation parameters calculated by Eyring equation are ΔH ∗ = 74.48 (±0.33) kJ mol−1; ΔS ∗ = −60.49 (±1.11) JK−1 mol−1 for anation and ΔH = −9.00 (±0.43) kJ mol−1; ΔS = −13.60(±1.42) KJ−1 mol−1 for ion-pairing.

Published
1978

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