• Kuheli Biswas

      Articles written in Journal of Biosciences

    • Role of ureogenesis in tackling problems of ammonia toxicity during exposure to higher ambient ammonia in the air-breathing walking catfishclarias batrachus

      Nirmalendu Saha Shritapa Datta Kuheli Biswas Zaiba Y Kharbuli

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      In the present study, the possible role of ureogenesis to avoid the accumulation of toxic ammonia to a lethal level under hyper-ammonia stress was tested in the air-breathing walking catfishClarias batrachus by exposing the fish at 25 mM NH4Cl for 7 days. Excretion of ammonia by the NH4Cl-exposed fish was totally suppressed, which was accompanied by significant accumulation of ammonia in different body tissues. The walking catfish, which is otherwise predominantly ammoniotelic, turned totally towards ureotelism from ammoniotelism with a 5-to 6-fold increase of urea-N excretion during exposure to higher ambient ammonia. Stimulation of ureogenesis was accompanied with significant increase of some of the key urea cycle enzymes such as carbamyl phosphate synthetase (urea cycle-related), argininosuccinate synthetase and argininosuccinate lyase both in hepatic and non-hepatic tissues. Due to this unique physiological strategy of turning towards ureotelism from ammoniotelism via the induced urea cycle, this air-breathing catfish is able to survive in very high ambient ammonia, which they face in certain seasons of the year in the natural habitat.

    • Cell volume changes affect gluconeogenesis in the perfused liver of the catfishClarias batrachus

      Carina Goswami Shritapa Datta Kuheli Biswas Nirmalendu Saha

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      In addition to lactate and pyruvate, some amino acids were found to serve as potential gluconeogenic substrates in the perfused liver ofClarias batrachus. Glutamate was found to be the most effective substrate, followed by lactate, pyruvate, serine, ornithine, proline, glutamine, glycine, and aspartate. Four gluconeogenic enzymes, namely phosphoenolpyruvate carboxykinase (PEPCK), pyruvate carboxylase (PC), fructose 1,6-bisphosphatase (FBPase) and glucose 6-phosphatase (G6Pase) could be detected mainly in liver and kidney, suggesting that the latter are the two major organs responsible for gluconeogenic activity in this fish. Hypo-osmotically induced cell swelling caused a significant decrease of gluconeogenic efflux accompanied with significant decrease of activities of PEPCK, FBPase and G6Pase enzymes in the perfused liver. Opposing effects were seen in response to hyperosmotically induced cell shrinkage. These changes were partly blocked in the presence of cycloheximide, suggesting that the aniso-osmotic regulations of gluconeogenesis possibly occurs through an inverse regulation of enzyme proteins and/or a regulatory protein synthesis in this catfish. In conclusion, gluconeogenesis appears to play a vital role inC. batrachus in maintaining glucose homeostasis, which is influenced by cell volume changes possibly for proper energy supply under osmotic stress.

    • Mean residence times of TF-TF and TF-miRNA toggle switches


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      Toggle switch networks are the simplest possible circuits with the ability of making a decision related to cell differentiation during embryonic development and disease progression. A common occurrence of toggle switch circuits is in the epithelial–mesenchymal transition (EMT) and its reverse, the mesenchymal–epithelial transition (MET), pathways which play key roles in phenotypic plasticity during cancer metastasis and therapy resistance. Recent studies have shown that the cells attaining one or more hybrid epithelial/mesenchymal (E/M) phenotypes during EMT/MET are more aggressive than those in either the epithelial or mesenchymal phenotype. In this work we studied the stability of each phenotype for different toggle switch circuits. We considered two-component toggle switch networks comprising either two mutually inhibiting transcription factors (TF-TF) or a TF-microRNA (TF-miR) chimera pair, and from Langevin dynamics, we determined the mean residence time (MRT) of cell phenotypes. MRT can be considered to be an indicator of stability in each cell phenotype and we showed that by replacing one of the TFs of the TF-TF toggle switch with miRNA generically stabilizes the hybrid phenotype. However, in the absence [presence] of a monostable hybrid state, the miRNA with faster [slower] degradation will make the hybrid state more probable. These results help to understand the implications of TF-TF and TF-miR circuits in the dynamics of cell fate decisions.

  • 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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