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Dr. N. Saha



Name:  Dr. Nirmalendu Saha, Ph.D

Designation:  Professor of Zoloogy

Specialization:  Biochemical Adaptation and Metabolic Regulation


Contact Information:

Biochemical Adaptation Laboratory
Department of Zoology,
North-Eastern Hill University
Shillong 793022, INDIA

Tel.: +91 364 272 2322 (work), +91 364 2550752 (home), +91-9436100836 (mobile)
Fax: +91 364 2550076



Academic Qualifications:




B. Sc.


North-Eastern Hill University, Shillong

M. Sc.


North-Eastern Hill University, Shillong

Ph. D.


North-Eastern Hill University, Shillong




  • Elected Fellow of National Academy of Sciences, India (F.N.A.Sc.)
  • Elected Fellow of Zoological Society, Kolkata (F.Z.S)
  • Awarded the ISCA Young Scientists Award by the Indian Science Congress Association in the year 1990
  • Awarded the Young Scientist Best Speaker Prize and a gold medal by the Ichthyological Society of India for the year 1987
  • Awarded the National Merit Scholarship from Matriculation up to M.Sc.


  • Awarded the Junior DAAD Fellowship  for two years and four months (June 1, 1991 to September 1993)
  • Awarded the Senior DAAD  Fellowship for three months (October 1 to December 31, 1997)
  • Worked as a Visiting Scientist (BAT II) on invitation in the laboratory of Professor Dr. D. Häussinger, Germany in a collaborative project  for one year (May 1, 2001 to April 2002)
  • Awarded the Senior DAAD Fellowship for two months (December 1, 2005 to January 31, 2006)


Memberships of academic societies, etc.:

  • Life Member of the National Academy of Sciences, Allahabad, India
  • Life member of the Indian Science Congress Association, Kolkata
  • Life Member of the Indian Society of Biological Chemists
  • Life Member of Zoological Society, Kolkata
  • Life Member of the Indian Society of Comparative Animal Physiologists

Major areas of research:

  • Nitrogen metabolism in air-breathing teleosts with special reference to ornithine-urea cycle (OUC) and amino acid metabolism under various environmental constraints.
  • Molecular mechanisms of regulation of ureogenesis and amino acid metabolism under environmental constraints in air-breathing teleosts.
  • Molecular characterisation of different OUC and amino acid metabolism-related genes in air-breathing teleosts.
  • Nitrogen and carbohydrate metabolism, oxidative stress and protein turnover with relation to cell volume changes in air-breathing teleosts.
  • Cell volume changes and early immediate gene expression in the hepatocytes of air-breathing teleosts.
  • Molecular characterization and regulation of expression of different nitric oxide synthase genes and the role of nitric oxide under environmental stresses in air-breathing teleosts.
  • Oxidative stress and antioxidant properties of air-breathing teleosts under environmental stresses.
  • Influence of nanoparticles on oxidative stress and antioxidant properties in air-breathing teleosts.

Most significant research contribution made by Prof. N. Saha and his group:

Prof. Saha and his group has shown for the first time the presence of a functional ornithine-urea (o-u) cycle in some freshwater air-breathing teleosts that are predominantly available in Indian subcontinent, such as Heteropneustes fossilisClarias batrachusAnabas spp. and Monopterus cuchia (Saha and Ratha, 1987, 1989; Saha et al., 1999), which otherwise was known to be non-functional or absent in all freshwater teleosts. This unique finding by Prof. Saha has contradicted the earlier “gene deletion” hypothesis proposed by Brown and Cohen (Biochem. J., 75: 82-91, 1960) based on their findings on non-occurrence of functional o-u cycle in teleosts. According to this hypothesis, some of the genes responsible for synthesis of o-u cycle enzyme proteins got deleted in the process of evolution of teleosts from marine to the freshwater habitat, since the osmotic problem reversed in the freshwater habitat compared to the marine counterpart. Prof. Saha has also shown, as a unique adaptation, that the functional o-u cycle could be stimulated at least in two air-breathing catfishes (C. batrachus and H. fossilis) under various environmental stresses, which they face in their natural habitat,  such as while living inside the mud-peat for months during the drought season (Saha et al., 2001), during exposure to higher ambient ammonia (Saha and Ratha, 1990, 1994; Saha and Das, 1999; Saha et al., 1995, 2003, 2007), and also to alkaline environment (Saha et al., 2002),  thus leading to a switch over from ammoniotelic mode of nitrogen excretion to ureotelic one. This unique adaptation, found generally in amphibians, was not reported earlier in any teleost species. Furthermore, Prof. Saha has also shown the existence of a functional o-u cycle in extra-hepatic tissues such as kidney, intestine and muscle in some of these air-breathing fishes (Saha and Ratha, 1987, 1989; Saha et al., 1999). Prof. Saha has also shown that C. batrachus has the capacity to convert very efficiently the toxic ammonia, generated endogenously or coming from external sources, to glutamine and various non-essential free amino acids (Saha et al., 2000, 2002, 2007) as another physiological strategies to tolerate a very high external ammonia. Thus, due to possessing all these unique biochemical adaptational flexibilities related to nitrogen metabolism, these air-breathing fishes, found mostly in Indian sub-continent, are able to live successfully for months inside the mud-peat under semidry conditions and also in polluted environment faced regularly by them, which are otherwise totally uninhabitable to any typical freshwater teleosts. Furthermore, his group has recently demonstrated that the o-u cycle enzymes gets expressed at a very early stage of life cycle, which can also be induced under high external ammonia (Kharbuli et al., 2006)

Another unique observation made by Prof. Saha and his group, is the presence of the o-u cycle-related carbamyl phosphate synthetase        I (CPS I) activity, which is normally present in higher vertebrates such as in mammals and amphibians, in addition to the presence of a typical fish type CPS III activity in two air-breathing teleosts (H. fossilis and C. batrachus) (Saha et al., 1997, 1999, 2007). This is again the first report of the presence of both types of o-u cycle-related CPSes (CPS I and III) in a single vertebrate species, which is otherwise normally not present together in a single vertebrate species. It was suggested that glutamine- and N-acetyl glutamate (NAG)-dependent CPS III, found in lower vertebrates, is the evolutionary precursor to ammonia- and NAG-dependent CPS I of ureotelic mammalian and amphibian species (Mommsen and Walsh, 1989, Science, 243: 72-75). Thus, the presence of both types of o-u cycle-related CPS activities in these air-breathing catfish has evolutionary significance with relation to the evolution of o-u cycle in vertebrates, in addition to their physiological significance.

Prof. Saha has also shown that although the air-breathing catfish (C. batrachus) possesses very efficient cell volume regulatory mechanisms liver, the hepatic cells remain partly swollen or shrunken states during hypo- and hypertonic exposures, respectively (Goswami and Saha, 2006) that can influence the carbohydrate metabolism and oxidative stress in C. batrachus; the hepatic cell swelling leads to stimulation of glycogenesis and hexose monophosphate pathway, inhibition of glycogenesis, gluconeogenesis and less oxidative stress, while the reverse is true during cell shrinkage (Goswami and Saha, 1998; Saha and Goswami, 2004; Goswami et al.,2004). All these observations indicate that this air-breathing catfish also possesses various physiological and biochemical adaptational strategies related to carbohydrate metabolism, thus enabling them to survive under osmotic, hypoxic and other environmentally-related stress problems, which they face in their natural habitat.

Furthermore, Prof. Saha has shown that the hypotonic cell swelling in C. batrachus liver causes stimulation of protein synthesis, inhibition of proteolysis and less production of nitric oxide through the inducible nitric oxide synthase; whereas the reverse is true during hypertonic cell shrinkage.

Prof. Saha, in his postdoctoral research work in Germany in collaboration with Prof. Häussinger, has shown definitely that the cell volume changes is the major determinant for the microtubule-dependent bile acid excretion by rat liver; cell swelling causes stimulation and cell shrinkage causes inhibition of bile acid excretion (Häussinger et al., 1992, 1993). Furthermore, he has also shown that the activation of Ca2+-dependent protein kinase C is the major factor of stimulating liver cholestasis, and finally liver serosis due to inhibition of canalicular transport of bile acids from liver (Kubitz et al., 2004). During liver cholestasis induced by the lipopolysaccharide, the multidrug resistance proteins the multidrug resistance protein (MRP) 3 and 5 get up-regulated as against the down-regulation of MRP2 in rat hepatocytes (Donner et al., 2004)


Number of M. Phil. /Ph. D. produced:

Ph. D. : 14



Title of Ph. D. Thesis

Dr. Jacqueline Dkhar


Induction of urea cycle enzymes and characterization of arginase in a freshwater air-breathing teleosts, Heteropneustes fossilis Bloch.

Dr. Lipika Das


Role of ureogenesis in a freshwater air-breathing catfish, Clarias batrachus under different environmental constraints

Dr. Supiya Dutta


Amino acid metabolism in a freshwater air-breathing catfish Clarias batrachus under hyper-ammonia and osmotic stress.

Dr. Carina Goswami


Mechanism of cell volume regulation and the effects of cell volume changes on glucose metabolism and oxidative stress in perfused liver of freshwater
air-breathing walking catfish, Clarias batrachus.

Dr. Bidyadhar Das


Anthelmintic efficacy of Flemingia vestita: An in vitro study on carbohydrate metabolism in the cestode, Raillietina echinobothrida.

Dr. Zaiba Y. Kharbuli


Purification and characterization of the urea cycle related carbamyl phosphate synthetase(s) and expression of urea cycle enzymes in a ureogenic air-breathing catfish, Clarias batrachus during early life stages.

Dr. Arundhati Bhattacharjee


Studies on nitrogen metabolism in an air-breathing catfish, Clarias batrachus during osmotic stress.

Dr. Shritapa Datta


Purification and characterization of glutamine synthetase and its regulation under various environmental stresses in an air-breathing catfish (Clarias batrachus).

Dr. Kuheli Biswas


Biochemical characterization of nitric oxide synthases, nitric oxide production and protein turnover during cell volume changes in the hepatocytes of air-breathing catfish, Clarias batrachus.

Dr. Jamesteword L. Khongsngi


Study of adaptive strategies against ammonia toxicity in the amphibious mud eel, Amphipnous cuchia.

Dr. Lucy M. Jyrwa


Effect of osmotic, hyper-ammonia and desiccation stresses on gluconeogenesis in the air-breathing catfish, Clarias batrachus.

Dr. Mahua G. Choudhury                2012

Regulation and molecular characterization of different isoforms of nitric oxide production under environmental stress in the air-breathing catfish, Heteropneustes fossilis.

Dr. Gitalee Bhuyan                 2013

Studies on tissue specific expression and induction of multiple glutamine synthetase genes under hyper-ammonia stress and ammonia-induced nitrotyrosynation of glutamine synthetase in catfish, Heteropneustes fossilis.

Dr. Manash Das                 2014

Effect of osmotic stress on gluconeogenesis and mitogen activated protein kinases in the air-breathing catfish (Heteropneustes fossilis).

M. Phil.: 1



Title of Thesis

Ms. Carina Goswami


Glucose efflux and the rate of gluconeogenesis in perfused liver of a freshwater air-breathing teleosts, Clarias batrachus during cell volume changes.


Number of Ph. D. students working for the degree: 6


Title of Ph. D. Dissertation

Ms. Hunlalliani

Influence of hyper-ammonia and dehydration stresses on the expression of multiple glutamine synthetase genes, heat shock protein 70 and mitogen-activated protein kinases in the mud eel, Monopterus cuchia.

Mr. Bodhisattwa Banerjee 

Studies on the influence of hyper-ammonia and desiccation stresses on the expression of mRNAs for ornithine-urea cycle enzymes, enzyme proteins and mitogen-activated protein kinases in the air-breathing catfish, Heteropneustes fossilis (Bloch)

Ms. Priyanka Lal

Studies on the influence of hyper-ammonia and desiccation stresses on the expression of mRNAs for ornithine-urea cycle enzymes, enzyme proteins and mitogen-activated protein kinases in the air-breathing catfish, Heteropneustes fossilis (Bloch)


Mr. Debaprasad Koner 

Effects of titanium dioxide and zinc oxide nanoparticles and their bulk counterparts on oxidative stress in the air-breathing catfish Clarias batrachus (Bloch)

Ms. Suman Kumari 

Effects of hyper-osmotic and hyper-ammonia stress on induction of genes for ornithine-urea cycle, amino acid metabolism-related enzymes and nitric oxide synthase in the air-breathing catfish Clarias batrachus (Bloch)

Ms. Rubaiya Hasan 

Environmentally-induced oxidative insults and antioxidant properties in air-breathing catfish, Clarias batrachus (Bloch)


Major Research Projects undertaken:

  1. Role of amino acid metabolism in Indian air-breathing teleosts to survive under hyper-ammonia stress.  GTZ, Germany. (1995-1999).
  2. Purification and characterization of carbamyl phosphate synthetase(s), and expression of urea cycle enzymes during early developmental stages in an amphibious potential ureogenic teleost, Clarias batrachus. UGC, New Delhi (2001-2004)
  3. Culture of carps and air-breathing fishes in hilly region and   transfer of technology to rural population of Meghalaya. DBT, New Delhi (2002-2005)
  4. Physiological significance of occurrence/expression and tissue distribution of nitric oxide synthases, production of nitric oxide under environmental constraints and pathological conditions in the air-breathing catfish, Heteropneustes fossilis. DST, New Delhi (2006-2009)
  5. Molecular and functional characterization of nitric oxide synthases and production of nitric oxide under environmental constraints and pathological conditions in the air-breathing catfish, Clarias batrachus. UGC, New Delhi (2007-2010)
  6. Influence of hyper-ammonia stress on the expression of multiple glutamine synthetase genes, mRNAs for ornithine urea cycle enzymes and mitogen activated protein kinases in air-breathing catfish, Heteropneustes fossilis.           DST, New Delhi (2010-2013)
  7. Molecular characterization in the expression of mRNAs for ornithine-urea cycle enzymes and enzyme proteins, multiple glutamine synthetase genes and signaling cascades under hyper-ammonia stress in the air-breathing walking catfish, Clarias batrachus. DBT Twining, New Delhi (2011-2015).
  8. Effects of high environmental ammonia on the expression of multiple glutamine synthetase genes, mitogen-activated protein kinases and Hsp70 in the air-breathing mud eel, Monopterus cuchia. UGC, New Delhi.
  9. Possible upregulation of ornithine-urea cycle genes and involvement of MAPKs to adapt under hyper-ammonia stress in air-breathing catfish, Clarias batrachus. DST-SERB, New Delhi


National: 12
International: 46 




Updated by lakmen_zoology on Aug 17, 2015 15:04:47