Vitamin B12-induced alterations in activities of α-glycerophosphate dehydrogenase and malic enzyme in brain of singi fish, Heteropneustes fossilis (Bloch)

Different doses of vitamin B₁₂ (0.25, 0.5, 1, 2 and 4 μg/g, injected intraperitoneally for three consecutive days) altered the activities of mitochondrial-α-glycerophosphate dehydrogenase (α-GPD) and NADP-dependent cytosolic malic enzyme (ME) in the brain of singi fish. The α-GPD activity increased at doses of 0.5, 1, 2 and 4 μg/g vitamin B₁₂. A dose of 0.5 μg/g vitamin B₁₂ induced less activity than higher doses. ME activity increased with 1, 2 and 4 μg/g of vitamin B₁₂/g. The mitochondrial and cytosolic protein content remained unchanged after vitamin B₁₂ administration. Cycloheximide treatment inhibited the vitamin B₁₂-induced increase in α-GPD and ME activity. Thus, vitamin B₁₂ is involved in the induction of some enzymes in fish brain.     

Changes in lipid peroxidation, superoxide dismutase activity, ascorbic acid and phospholipid content in liver of freshwater catfish Heteropneustes fossilis exposed to elevated temperature

1. 1. Lipid peroxidation, superoxide dismutase (SOD) activity, ascorbic acid (AsA) and individual phospholipid contents in liver of fresh water cat fish Heteropneustes fossilis were measured after exposure to different temperatures (25, 27, 32, 37°C) at various times (1–4 h).

2. 2. Lipid peroxidation and superoxide dismutase activity were significantly increased with increases in temperature at various times.

3. 3. Ascorbic acid content was depleted when temperature was increased.

4. 4. After temperature exposure, phosphatidyl inositol was increased while phosphatidyl choline, phosphatidyl serine and phosphatidyl ethanolamine were depleted. Phosphatidic acid level did not change.

5. 5. The findings indicated an increased oxidative stress in liver following increases in temperature at various times. Concurrent with the increase in lipid peroxidation, superoxide dismutase activity and ascorbic acid from the liver of fish varied. It is suggested that depletion of major individual phospholipids following temperature exposure could be due to superoxide created oxidative stress in the liver.

     

Purification and characterization of tubulin from the catfishHeteropneustes fossilis

Tubulin was purified from the brain of the catfishHeteropneustes fossilis by cycles of temperature-dependent assembly and disassembly. Fish tubulin assembles into microtubules in the absence of high molecular weight microtubule associated proteins. Its subunits comigrate with goat brain α andβ tubulin subunits and is composed of 4 major α andβ tubulins each as analyzed by isoelectric focusing and two dimensional gel electrophoresis. Peptide mapping showed it to be very similar to goat brain tubulin. Polymerization of catfish brain tubulin occurs optimally between 18–37°C and the critical protein concentrations of assembly at 18°C and 37°C are the same, as opposed to mammalian brain tubulins.     

Purification and immunological characterization of catfish (Heteropneustes fossilis) metallothionein

Summary Catfish hepatic metallothionein was purified to homogeneity by Sephadex G-75 gel filtration, DEAF-Sephadex A-25 column chromatography and preparative polyacrylamide gel electrophoresis. Induction by cadmium and zinc, characteristic UV spectrum, cadmium binding property and its low MW established that it was a metallothionein. Antibody was raised in rabbit against catfish metallothionein. Catfish antimetallothionein cross-reacted with other fish metallothioneins but not with chicken or rodent metallothionein. Catfish metallothionein is more electronegative as compared to mouse, rat, chicken or hamster metallothionein. Catfish MT appeared to aggregate readily on storage and to be less electronegative.Abbreviations MT Metallothionein - PBS Phosphate Buffered Saline - SDS Sodium Dodecyl Sulfat - PAGE Polyacrylamide Gel Electrophoresis Part of the work was reported in Proceedings of 54th Annual General Meeting of the Society of Biological Chemists, India, 1985.     

Does fish represent an intermediate stage in the evolution of ureotelic cytosolic arginase I?

Arginase catalyses the last step of the urea cycle. At least two isoenzymes of arginase are known; cytosolic ARG I and mitochondrial ARG II. ARG I is predominantly expressed in liver cytosol, as a part of urea cycle in ureotelic animals. The second isoform ARG II is primarily responsible for non-ureogenic functions, expressed in mitochondria of both hepatic and non-hepatic tissues in most vertebrates. Most micro-organisms and invertebrates are known to have only one type of arginase, whose function is unrelated to ornithine-urea cycle (OUC). However, in ureo-osmotic marine elasmobranchs arginase is localized in liver mitochondria as a part of OUC to synthesize urea for osmoregulation. An evolutionary transition occurred in arginase enzyme in terrestrial ureotelic vertebrates, with the evolution of ARG I from a pre-existing ancestral mitochondrial ARG II. This cytosolic ARG I activity is supposed to have first appeared in lung fishes, but the 40% and 60% distribution of arginase I and II activity in liver and kidney tissue of Heteropneustes fossilis indicates reconsideration of the above fact.     

Influence of temperature on ovarian recrudescence in the Indian catfish, Heteropneustes fossilis

Over a 60-day experiment during the preparatory phase of the reproductive cycle, ovarian weights increased with rise in temperature in Heteropneustes fossilis and oocyte diameters suggested an optimum temperature of 22° C for Stage II oocyte formation. The oocytes did not reach Stage II at 10° C. Atresia of Stage III oocytes occurred following 60 days of exposure at 30°C.     

Cloning, sequencing and expression of cDNA encoding growth hormone from Indian catfish (Heteropneustes fossilis)

A tissue-specific cDNA library was constructed using polyA⁺ RNA from pituitary glands of the Indian catfishHeteropneustes fossilis (Bloch) and a cDNA clone encoding growth hormone (GH) was isolated. Using polymerase chain reaction (PCR) primers representing the conserved regions of fish GH sequences the 3′ region of catfish GH cDNA (540 bp) was cloned by random amplification of cDNA ends and the clone was used as a probe to isolate recombinant phages carrying the full-length cDNA sequence. The full-length cDNA clone is 1132 bp in length, coding for an open reading frame (ORF) of 603 bp; the reading frame encodes a putative polypeptide of 200 amino acids including the signal sequence of 22 amino acids. The 5′ and 3′ untranslated regions of the cDNA are 58 bp and 456 bp long, respectively. The predicted amino acid sequence ofH. fossils GH shared 98% homology with other catfishes. Mature GH protein was efficiently expressed in bacterial and zebrafish systems using appropriate expression vectors. The successful expression of the cloned GH cDNA of catfish confirms the functional viability of the clone.     

Microsatellites from Clarias batrachus and their polymorphism in seven additional catfish species

We isolated 18 novel microsatellite loci from the walking catfish (Clarias batrachus), and examined their cross‐amplification in seven additional catfish species from three families. Sixteen of the 18 microsatellites were polymorphic in the source species (allele number: 2–10/locus and expected heterozygosity: 0.30–0.87). Moreover, nine of these 18 primer pairs cross‐amplified specific and polymorphic products from the genome of at least six of the seven other catfish species tested. However, the success rate of cross‐species amplification varied from locus to locus, indicating that cross‐species amplification of microsatellites is locus‐dependent.     

Alterations in air‐sac and skeleton of triploid Heteropneustes fossilis

Triploid stinging catfish Heteropneustes fossilis, when produced by cold shock, showed abnormalities in their air‐sacs and skeletons.