• F R Billimoria

      Articles written in Journal of Biosciences

    • Effect of experimentally induced thyrotoxicosis on oxidative energy metabolism in rat heart mitochondria

      S S Katyare F R Billimoria

      More Details Abstract Fulltext PDF

      Treatment of rats with T3 resulted in a significant decrease in body weight, while the heart weight increased. T4 treatment had less marked effect on body weights but resulted in decreased heart weights. Serum T4 levels decreased significantly with simultaneous increase of T3 level following T3 treatment, whereas with T4 treatment, levels of both T4 and T3 increased in the serum. Low doses of T3 (0.5 µg ) caused decrease in mitochondrial protein content while high dose of T4 (1 µg), caused significant increase in mitochondrial mass. The state 3 respiration rates were significantly depressed following T3 and T4 treatments, in a substrate specific manner with the effects being more pronounced with T3; these responses with T4 were dose-dependent for succinate and ascorbate + N,N,N′,N′-tetramethyl-p-phenylenedíamme. State 4 respiration rates also exhibited similar corresponding changes. ADP/O ratios were not changed but ADP-phosphorylation rates were decreased significantly particularly so with the T3-treated animals. Treatment with T3 also resulted in lowering of intramitochondrial cytochrome contents. Similar effects were seen also with higher doses of T4. The results thus indicate that T3- and T4- thyrotoxicosis results in impaired energy metabolism in heart mitochondria.

    • Altered kinetic properties of rat heart mitochondrial enzymes following experimental-thyrotoxicosis

      B N Dave F R Billimoria S S Katyare

      More Details Abstract Fulltext PDF

      Effects of T3- and T4-induced thyrotoxicosis on temperature-dependent Arrhenius kinetics of succinate oxidase and Mg2+- and Mg2+ + 2,4-dinitrophenol-dependent ATPase activities in rat heart mitochondria were examined, For succinate oxidase system, treatment with T3 and T4 caused increase in the energy of activation in high temperature range in a dose-dependent manner. For low temperature range, increase in energy of activation was apparent only with higher doses of the hormones; with low doses a small but reproducible decrease was evinced. The phase transition temperature decreased significantly under these conditions. For the Mg2+- and Mg2++2,4-dintro-phenol-dependent-ATPase activities, the activation energy values in high temperature range decreased in general. Activation energy values in low temperature range recorded a generalized increase in the Mg2+-ATPase enzyme system while the value did not change significantly for the Mg2+ + 2,4-dinitrophenol-ATPase; phase transition temperature registered a small but reproducible decrease under these conditions. The results are suggestive of increased membrane fluidization possibly through increased proportion of unsaturated fatty acids. The differential effects seen for succinate oxidase and ATPase systems are consistent with different lipid protein domains of these enzyme systems.

  • Journal of Biosciences | News

      Forthcoming Special issue.

    • To trigger further research on plant mitochondria, the Journal of Biosciences is bringing out a special issue titled "Plant Mitochondria: Properties and Interactions with Other Organelles".

      Plant mitochondria are quite distinct and have unique features, such as a cyanide-insensitive alternate pathway. They also interact with chloroplasts to optimize photosynthetic carbon assimilation.

      Submissions are welcome until 30 July 2023. The contributions can be original articles, short communications, reviews, or mini-reviews on any topic related to plant mitochondria.

      Authors can submit their articles online at https://www.editorialmanager.com/jbsc/default2.aspx

      Posted on April 12, 2023
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      Posted on July 25, 2019

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